/* ==========================================================================
   intclass — minimal, flat, square-cornered UI
   One set of colour tokens drives both themes; components never hard-code
   light-only colours, so dark mode stays consistent.
   ========================================================================== */

:root {
  /* 60% white · 25% dark navy · 15% blue */
  --bg: #ffffff;
  --surface: #ffffff;
  --surface-subtle: #f5f7fb;
  --surface-hover: #edf1f8;
  --border: #e3e8f0;
  --border-strong: #cbd5e1;

  --ink: #0b1220;
  --soft: #475569;
  --faint: #64748b;

  --accent: #2563eb;
  --accent-strong: #1d4ed8;
  --accent-text: #2563eb;
  --on-accent: #ffffff;
  --accent-soft: #eff6ff;
  --accent-tint: #dbeafe;
  --accent-border: #bfdbfe;
  --accent-glow: rgba(37, 99, 235, 0.32);
  --accent-gradient: linear-gradient(135deg, #3b82f6 0%, #2563eb 52%, #1d4ed8 100%);
  --hero-glow: radial-gradient(closest-side, rgba(37, 99, 235, 0.16), rgba(37, 99, 235, 0));
  --head-glow: radial-gradient(closest-side, rgba(96, 165, 250, 0.38), rgba(96, 165, 250, 0));
  --blue-band: #eff6ff;
  --blue-band-border: #bfdbfe;
  --band-end: #12306e;

  --math: #2563eb;
  --rus: #0284c7;

  /* dark navy bands: curriculum, lessons heading, footer */
  --band-bg: #0b1220;
  --band-surface: #111a2e;
  --band-surface-2: #16213a;
  --band-border: #1e2a44;
  --band-border-strong: #334466;
  --band-ink: #f8fafc;
  --band-soft: #a7b4c9;
  --band-faint: #8796ad;
  --band-accent-text: #6ea8ff;
  --band-accent-soft: #13254d;
  --band-accent-border: #1e3a8a;

  --success: #15803d;
  --success-soft: #f0fdf4;
  --success-border: #bbf7d0;
  --danger: #dc2626;
  --danger-soft: #fef2f2;
  --danger-border: #fecaca;

  --overlay: rgba(11, 18, 32, 0.5);
  --media-ui: rgba(11, 18, 32, 0.62);

  /* drawings in quiz tasks: the palette of the «за минуту» videos */
  --fig-paper: #f7f9fc;
  --fig-grid: #e1e7f0;
  --fig-teal: #1e8c78;
  --fig-teal-soft: rgba(30, 140, 120, 0.22);
  --fig-mustard: #f0b23a;
  --fig-mustard-soft: rgba(240, 178, 58, 0.26);
  --fig-teal-mid: rgba(30, 140, 120, 0.42);
  --fig-red-soft: rgba(225, 81, 58, 0.2);
  --fig-red: #e1513a;
  --fig-on-color: #1d1b2e;
  --fig-ok-soft: rgba(22, 163, 74, 0.2);

  --radius-sm: 6px;
  --radius: 8px;
  --radius-lg: 12px;

  /* Unbounded (made for Cyrillic) carries the headings, Onest the reading text */
  --font-display: "Unbounded", "Onest", system-ui, sans-serif;
  --font-body: "Onest", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;

  --header-h: 60px;
  --ease: cubic-bezier(0.2, 0, 0, 1);
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --spring: cubic-bezier(0.34, 1.56, 0.64, 1);
  --fast: 160ms;
  --medium: 260ms;

  color-scheme: light;
}

:root[data-theme="dark"] {
  /* charcoal greys with a faint cool cast, one flat blue: no navy, no gradients, no glow */
  --bg: #0f1013;
  --surface: #16171b;
  --surface-subtle: #1b1d21;
  --surface-hover: #222429;
  --border: #26282d;
  --border-strong: #383b42;

  --ink: #ededef;
  --soft: #a9acb4;
  --faint: #8b8e97;

  --accent: #2563eb;
  --accent-strong: #3b82f6;
  --accent-text: #7aa7f7;
  --on-accent: #ffffff;
  --accent-soft: #1a2131;
  --accent-tint: #1f2a44;
  --accent-border: #2e4372;
  --accent-glow: rgba(0, 0, 0, 0.55);
  --accent-gradient: #2563eb;
  --hero-glow: transparent;
  --head-glow: transparent;
  --blue-band: #141518;
  --blue-band-border: #2c2e34;
  --band-end: #0b0c0e;

  --math: #7aa7f7;
  --rus: #5cc0ee;

  --band-bg: #0b0c0e;
  --band-surface: #141518;
  --band-surface-2: #1a1b1f;
  --band-border: #222428;
  --band-border-strong: #33363c;
  --band-ink: #ededef;
  --band-soft: #a9acb4;
  --band-faint: #8b8e97;
  --band-accent-text: #7aa7f7;
  --band-accent-soft: #1a2131;
  --band-accent-border: #2e4372;

  --success: #4ade80;
  --success-soft: #0d1f14;
  --success-border: #14532d;
  --danger: #f87171;
  --danger-soft: #2a1213;
  --danger-border: #7f1d1d;

  --overlay: rgba(0, 0, 0, 0.6);
  --media-ui: rgba(0, 0, 0, 0.62);

  --fig-paper: #121316;
  --fig-grid: #25272c;
  --fig-teal: #34b89c;
  --fig-teal-soft: rgba(52, 184, 156, 0.24);
  --fig-mustard: #f2be52;
  --fig-mustard-soft: rgba(242, 190, 82, 0.24);
  --fig-teal-mid: rgba(52, 184, 156, 0.42);
  --fig-red-soft: rgba(242, 112, 90, 0.22);
  --fig-red: #f2705a;
  --fig-on-color: #10131c;
  --fig-ok-soft: rgba(74, 222, 128, 0.2);

  color-scheme: dark;
}

/* Dark navy bands reuse every component with darker tokens */
.section-dark,
.page-head,
.footer {
  --bg: var(--band-bg);
  --surface: var(--band-surface);
  --surface-subtle: var(--band-surface-2);
  --surface-hover: var(--band-surface-2);
  --border: var(--band-border);
  --border-strong: var(--band-border-strong);
  --ink: var(--band-ink);
  --soft: var(--band-soft);
  --faint: var(--band-faint);
  --accent-text: var(--band-accent-text);
  --accent-soft: var(--band-accent-soft);
  --accent-border: var(--band-accent-border);
  background: var(--bg);
  color: var(--ink);
}

/* Light-blue band: same components on a blue-tinted ground */
.section-blue {
  --border: var(--blue-band-border);
  background: var(--blue-band);
}

.section-dark,
.section-blue {
  border-bottom: 0;
}

/* ==========================================================================
   Base
   ========================================================================== */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-h) + 12px);
}

body {
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.6;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  -webkit-tap-highlight-color: transparent;
  overflow-x: hidden;
  overflow-x: clip;
}

body.modal-open,
body.menu-open {
  overflow: hidden;
}

::selection {
  background: var(--accent);
  color: var(--bg);
}

img,
svg,
video {
  display: block;
  max-width: 100%;
}

a {
  color: inherit;
  text-decoration: none;
}

button,
input {
  font: inherit;
  color: inherit;
}

button {
  cursor: pointer;
  background: none;
  border: 0;
}

a,
button,
input,
label {
  touch-action: manipulation;
}

h1,
h2,
h3 {
  line-height: 1.15;
  letter-spacing: -0.02em;
  overflow-wrap: break-word;
  text-wrap: balance;
}

h1,
h2,
.logo,
.stat-number {
  font-family: var(--font-display);
  font-weight: 700;
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

[hidden] {
  display: none !important;
}

.container {
  width: min(1120px, 100% - 2.5rem);
  margin-inline: auto;
}

/* Scroll-reveal hooks are kept in the markup but no longer animate */
.reveal-line {
  display: block;
}

/* ==========================================================================
   Buttons
   ========================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45rem;
  min-height: 44px;
  padding: 0.6rem 1.15rem;
  border: 1px solid var(--accent);
  border-radius: var(--radius);
  background: var(--accent-gradient);
  color: var(--on-accent);
  font-size: 0.95rem;
  font-weight: 600;
  line-height: 1.2;
  text-align: center;
  white-space: nowrap;
  transition: opacity var(--fast) var(--ease), background var(--fast) var(--ease),
    transform var(--medium) var(--ease-out), box-shadow var(--medium) var(--ease-out);
}

.btn-small {
  min-height: 38px;
  padding: 0.45rem 0.9rem;
  font-size: 0.88rem;
}

.btn-ghost,
.btn-secondary {
  background: transparent;
  color: var(--ink);
  border-color: var(--border-strong);
}

/* ==========================================================================
   Header
   ========================================================================== */
.nav {
  position: sticky;
  top: 0;
  z-index: 60;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  padding-top: env(safe-area-inset-top, 0px);
  will-change: transform;
  transition: transform 460ms var(--ease-out), box-shadow 300ms var(--ease);
}

.nav.scrolled {
  box-shadow: 0 10px 30px -24px rgba(11, 18, 32, 0.55);
}

/* slid out of view while reading; main.js brings it back on scroll up */
.nav.nav-hidden {
  transform: translateY(-105%);
  box-shadow: none;
  pointer-events: none;
  transition-duration: 340ms;
  transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
}

.nav-inner {
  display: flex;
  align-items: center;
  gap: 1rem;
  height: var(--header-h);
}

.logo {
  display: inline-flex;
  align-items: baseline;
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  white-space: nowrap;
}

.logo-dot {
  width: 6px;
  height: 6px;
  margin-left: 3px;
  border-radius: 2px;
  background: var(--accent);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  margin-left: auto;
}

.nav-link {
  display: inline-flex;
  align-items: center;
  font-size: 0.92rem;
  font-weight: 500;
  color: var(--soft);
  transition: color var(--fast) var(--ease);
}

.nav-link.active {
  color: var(--ink);
}

.nav-link-arrow,
.nav-mobile-header,
.nav-quick-subjects,
.nav-mobile-footer {
  display: none;
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.theme-toggle-btn,
.nav-profile-btn,
.burger {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  min-width: 40px;
  height: 40px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  font-size: 0.9rem;
  font-weight: 500;
  transition: border-color var(--fast) var(--ease), background var(--fast) var(--ease);
}

.theme-icon {
  display: inline-flex;
}

.theme-icon svg {
  width: 18px;
  height: 18px;
}

.nav-profile-btn,
.burger {
  display: none;
}

/* level on the profile button */
.profile-level {
  position: absolute;
  top: 2px;
  right: 2px;
  display: grid;
  place-items: center;
  min-width: 15px;
  height: 15px;
  padding: 0 3px;
  border-radius: 8px;
  background: var(--accent-gradient);
  color: var(--on-accent);
  font-family: var(--font-display);
  font-size: 0.56rem;
  font-weight: 700;
  line-height: 1;
}

.burger span {
  position: absolute;
  left: 50%;
  width: 18px;
  height: 2px;
  margin-left: -9px;
  background: currentColor;
  transition: transform var(--fast) var(--ease), opacity var(--fast) var(--ease);
}

.burger span:nth-child(1) { top: 13px; }
.burger span:nth-child(2) { top: 19px; }
.burger span:nth-child(3) { top: 25px; }

.burger.open span:nth-child(1) { transform: translateY(6px) rotate(45deg); }
.burger.open span:nth-child(2) { opacity: 0; }
.burger.open span:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }

.nav-backdrop {
  display: none;
}

/* ==========================================================================
   Home: hero
   ========================================================================== */
.hero {
  position: relative;
  display: flex;
  align-items: center;
  /* the first screen fills the viewport, so the next section never peeks in */
  min-height: calc(100vh - var(--header-h));
  min-height: calc(100svh - var(--header-h) - env(safe-area-inset-top, 0px));
  padding: clamp(3rem, 8vw, 5rem) 0 clamp(7.5rem, 16vh, 9rem);
  border-bottom: 1px solid var(--border);
}

/* soft blue glow behind the first screen; drifts slowly when motion is allowed */
.hero {
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  right: -28%;
  top: 6%;
  width: min(92vw, 760px);
  aspect-ratio: 1;
  background: var(--hero-glow);
  pointer-events: none;
}

.hero-inner {
  position: relative;
  z-index: 1;
}

.hero-eyebrow,
.section-label {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-text);
}

.hero-title {
  margin: 0.9rem 0 1.1rem;
  font-size: clamp(2.1rem, 8vw, 4.2rem);
  font-weight: 700;
  letter-spacing: -0.035em;
  line-height: 1.06;
}

.hero-invert {
  position: relative;
  isolation: isolate;
  display: inline-block;
  margin-top: 0.08em;
  /* the words have no tall letters, only the tail of «у»: a tight line and more padding
     below keep the letters optically centred and the tail inside the box; the right side
     is wider because «у» overhangs its own advance, so both sides look the same */
  padding: 0.15em 0.21em 0.31em 0.15em;
  line-height: 0.66;
  border-radius: 10px;
  background: var(--accent-gradient);
  color: var(--on-accent);
}

/* Where supported, the box is trimmed to the lowercase letters themselves (x-height to
   baseline), so equal padding centres them exactly at every size and in any font */
@supports (text-box: trim-both ex alphabetic) {
  .hero-invert {
    padding-block: 0.29em;
    line-height: 1;
    text-box: trim-both ex alphabetic;
  }
}

.hero-sub {
  max-width: 34rem;
  font-size: clamp(1rem, 2.6vw, 1.15rem);
  color: var(--soft);
}

.hero-actions {
  margin-top: 1.75rem;
}

.hero-actions > span {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
}

/* «Листайте вниз»: a finger swipes up on touch screens, a mouse wheel rolls on computers */
.scroll-hint {
  position: absolute;
  left: 50%;
  bottom: clamp(1.25rem, 4vh, 2.5rem);
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 0.25rem 1rem;
  border-radius: var(--radius);
  transform: translateX(-50%);
  color: var(--accent-text);
  transition: opacity 0.45s var(--ease), transform 0.45s var(--ease-out);
}

.scroll-hint-icon {
  position: relative;
  display: grid;
  place-items: center;
  width: 44px;
  height: 58px;
}

.scroll-hint-icon svg {
  width: 30px;
  height: 30px;
}

/* the trail the finger leaves while swiping */
.scroll-hint-finger::before {
  content: "";
  position: absolute;
  left: 50%;
  top: 4px;
  bottom: 10px;
  width: 2px;
  margin-left: -1px;
  border-radius: 2px;
  background: linear-gradient(to top, var(--accent), transparent);
  opacity: 0.35;
}

.scroll-hint-mouse {
  display: none;
}

.scroll-hint-mouse svg {
  width: 24px;
  height: 36px;
}

.has-scrolled .scroll-hint {
  opacity: 0;
  pointer-events: none;
  transform: translate(-50%, 14px);
}

/* ==========================================================================
   Sections & cards
   ========================================================================== */
.section {
  padding: clamp(6rem, 16vw, 10rem) 0;
  border-bottom: 1px solid var(--border);
}

/* Home page: one section per screen. Each section fills the screen minus a thin strip, so at
   its start you see only this section and the top edge of the next one. Gentle snapping settles
   the scroll on section starts, so the previous section is never left half on screen. */
html:has(> body.home-page) {
  scroll-snap-type: y proximity;
  scroll-padding-top: 0;
}

.home-page {
  --peek: clamp(56px, 9vh, 96px);
}

.home-page .hero {
  scroll-snap-align: start;
  /* the sticky header sits above the hero: a margin taller than the header clamps this snap point
     to the very top of the page, whatever the header's exact height */
  scroll-margin-top: 50vh;
}

.home-page main > .section {
  display: flex;
  flex-direction: column;
  justify-content: center;
  min-height: calc(100vh - var(--peek));
  min-height: calc(100svh - var(--peek));
  padding-block: clamp(3rem, 7vh, 5.5rem);
  scroll-snap-align: start;
}

.home-page main > .section .section-head {
  margin-bottom: clamp(1.75rem, 4vh, 2.75rem);
}

.section-head {
  max-width: 42rem;
  margin-bottom: clamp(2.5rem, 7vw, 3.75rem);
}

.section-title {
  margin: 0.5rem 0 0.6rem;
  font-size: clamp(1.6rem, 5vw, 2.3rem);
  font-weight: 700;
}

.section-desc {
  color: var(--soft);
}

.grid {
  display: grid;
  gap: 1.25rem;
}

.card {
  display: block;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--surface);
  transition: border-color var(--fast) var(--ease), transform var(--medium) var(--ease-out),
    box-shadow var(--medium) var(--ease-out);
}

.subjects-grid,
.subject-detail-grid {
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 320px), 1fr));
}

.subject-card {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1.25rem;
}

.subject-icon,
.choice-icon {
  display: grid;
  place-items: center;
  flex: none;
  width: 44px;
  height: 44px;
  border: 1px solid var(--accent-border);
  border-radius: var(--radius);
  background: var(--accent-soft);
  font-size: 1.2rem;
  font-weight: 700;
}

.subject-icon {
  border-color: var(--accent);
  background: var(--accent-gradient);
  color: var(--on-accent);
}

[data-subject="math"] .choice-icon {
  color: var(--math);
}

[data-subject="russian"] .choice-icon {
  color: var(--rus);
}

.subject-card-body {
  flex: 1;
  min-width: 0;
}

.subject-card h3 {
  font-size: 1.1rem;
  margin-bottom: 0.2rem;
}

.subject-card-desc {
  font-size: 0.9rem;
  color: var(--soft);
}

.card-arrow {
  color: var(--faint);
  transition: transform var(--fast) var(--ease), color var(--fast) var(--ease);
}

.subject-detail-card {
  display: flex;
  flex-direction: column;
  padding: 1.5rem;
}

.subject-detail-badge {
  align-self: flex-start;
  margin-bottom: 1rem;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--faint);
}

.subject-detail-card h3 {
  font-size: 1.25rem;
  margin-bottom: 0.5rem;
}

.subject-detail-lead {
  color: var(--soft);
  margin-bottom: 1rem;
}

.subject-points-list {
  list-style: none;
  display: grid;
  gap: 0.6rem;
  margin-bottom: 1.5rem;
  font-size: 0.92rem;
  color: var(--soft);
}

.subject-points-list li {
  padding-left: 1rem;
  position: relative;
}

.subject-points-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.62em;
  width: 5px;
  height: 5px;
  border-radius: 1px;
  background: var(--accent);
}

.subject-points-list strong {
  color: var(--ink);
  font-weight: 600;
}

.subject-card-footer {
  margin-top: auto;
}

.grades-guide-grid {
  gap: 0;
  border-top: 1px solid var(--border);
}

.grade-guide-item {
  display: grid;
  grid-template-columns: minmax(0, 15rem) minmax(0, 1fr);
  gap: 0.4rem 2rem;
  padding: 1.6rem 0;
  border-bottom: 1px solid var(--border);
}

.grade-guide-header {
  display: grid;
  gap: 0.3rem;
}

.grade-tag {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-text);
}

.grade-guide-header strong {
  font-weight: 600;
  line-height: 1.35;
}

.grade-guide-item p {
  color: var(--soft);
  font-size: 0.95rem;
}

.center-actions {
  display: flex;
  justify-content: center;
  margin-top: 3rem;
}

/* ==========================================================================
   Footer
   ========================================================================== */
.footer {
  padding: 2.5rem 0 calc(2.5rem + env(safe-area-inset-bottom, 0px));
}

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem 1.5rem;
}

.footer-text,
.footer-link {
  font-size: 0.85rem;
  color: var(--faint);
}

.footer-link {
  padding: 0.5rem 0;
  transition: color var(--fast) var(--ease);
}

.footer-link:hover {
  color: var(--ink);
}

/* ==========================================================================
   Profile modal
   ========================================================================== */
.modal-backdrop {
  position: fixed;
  inset: 0;
  z-index: 100;
  display: grid;
  place-items: center;
  padding: 1.25rem;
  background: var(--overlay);
}

.modal {
  position: relative;
  width: min(440px, 100%);
  max-height: calc(100vh - 2.5rem);
  max-height: calc(100dvh - 2.5rem);
  overflow-y: auto;
  padding: 1.75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--surface);
}

.sheet-handle {
  display: none;
}

.modal-close {
  position: absolute;
  top: 0.75rem;
  right: 0.75rem;
  width: 40px;
  height: 40px;
  border-radius: var(--radius);
  font-size: 1.5rem;
  line-height: 1;
  color: var(--soft);
}

.modal h2 {
  margin: 0.4rem 0 0.5rem;
  font-size: 1.45rem;
  font-weight: 700;
}

.modal-text {
  margin-bottom: 1.25rem;
  font-size: 0.92rem;
  color: var(--soft);
}

.modal form {
  display: grid;
  gap: 0.9rem;
}

.modal form label {
  display: grid;
  gap: 0.35rem;
  font-size: 0.85rem;
  font-weight: 600;
}

.modal form input {
  width: 100%;
  min-height: 46px;
  padding: 0.65rem 0.85rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--bg);
  font-size: 16px;
  outline: none;
}

.modal form input:focus {
  border-color: var(--accent);
}

.modal form input::placeholder,
.lesson-search-input::placeholder {
  color: var(--faint);
}

.form-status {
  min-height: 1.2em;
  margin-top: 0.6rem;
  font-size: 0.86rem;
  color: var(--soft);
}

.profile-stats-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.6rem;
  margin-top: 0.5rem;
}

.profile-stat-box {
  display: grid;
  gap: 0.15rem;
  padding: 0.85rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
}

.stat-number {
  font-size: 1.5rem;
  font-weight: 700;
  line-height: 1;
}

.stat-label {
  font-size: 0.8rem;
  color: var(--faint);
}

/* ==========================================================================
   Lessons page: heading, route, progress, search, filters
   ========================================================================== */
.page-head {
  position: relative;
  overflow: hidden;
  padding: clamp(3.5rem, 10vw, 6rem) 0 clamp(2.5rem, 6vw, 3.5rem);
  border-bottom: 1px solid var(--border);
  background: linear-gradient(155deg, var(--band-bg) 0%, var(--band-end) 100%);
}

/* soft blue glow in the corner of the library header */
.page-head::before {
  content: "";
  position: absolute;
  right: -22%;
  top: -70%;
  width: min(90vw, 640px);
  aspect-ratio: 1;
  background: var(--head-glow);
  pointer-events: none;
}

.page-head > .container {
  position: relative;
}

.page-title {
  margin: 0.5rem 0;
  font-size: clamp(2rem, 7vw, 3.2rem);
  font-weight: 700;
  letter-spacing: -0.04em;
}

.page-sub {
  color: var(--soft);
  max-width: 36rem;
}

.lessons-section {
  border-bottom: 0;
  padding-top: clamp(2rem, 6vw, 3rem);
}

.lesson-flow {
  display: grid;
  gap: 1.25rem;
}

.flow-progress {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.85rem;
  color: var(--faint);
}

.progress-caption {
  display: none;
}

.progress-step {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  white-space: nowrap;
}

.step-dot {
  display: grid;
  place-items: center;
  width: 22px;
  height: 22px;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 700;
}

.progress-step.active {
  color: var(--ink);
}

.progress-step.active .step-dot {
  border-color: var(--accent);
  color: var(--accent-text);
}

.progress-step.completed {
  color: var(--soft);
}

.progress-step.completed .step-dot {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--on-accent);
}

.progress-divider {
  flex: 1;
  height: 1px;
  min-width: 12px;
  background: var(--border);
}

.overall-progress-card {
  padding: 0.9rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
}

.overall-progress-header {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.25rem 1rem;
  margin-bottom: 0.6rem;
}

.overall-progress-title {
  font-size: 0.88rem;
  font-weight: 600;
}

.overall-progress-text {
  font-size: 0.82rem;
  color: var(--faint);
  font-variant-numeric: tabular-nums;
}

.progress-bar-track {
  height: 4px;
  background: var(--surface-hover);
}

.progress-bar-track {
  border-radius: 999px;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  border-radius: 999px;
  background: var(--accent);
  transition: width 0.8s var(--ease-out);
}

.search-input-wrap {
  position: relative;
  display: flex;
  align-items: center;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  transition: border-color var(--fast) var(--ease);
}

.search-input-wrap:focus-within {
  border-color: var(--accent);
}

.search-icon-svg {
  position: absolute;
  left: 0.85rem;
  color: var(--faint);
  pointer-events: none;
}

.lesson-search-input {
  width: 100%;
  min-height: 48px;
  padding: 0.7rem 3rem 0.7rem 2.6rem;
  border: 0;
  outline: none;
  background: transparent;
  font-size: 16px;
  -webkit-appearance: none;
  appearance: none;
}

.lesson-search-input::-webkit-search-cancel-button {
  -webkit-appearance: none;
}

.search-kbd-hint {
  position: absolute;
  right: 0.85rem;
  padding: 0.1rem 0.45rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: inherit;
  font-size: 0.75rem;
  color: var(--faint);
  pointer-events: none;
}

.clear-search-btn {
  position: absolute;
  right: 4px;
  width: 40px;
  height: 40px;
  border-radius: var(--radius);
  color: var(--soft);
}

.filter-tabs-bar {
  display: flex;
  gap: 0.4rem;
  overflow-x: auto;
  scrollbar-width: none;
}

.filter-tabs-bar::-webkit-scrollbar {
  display: none;
}

.filter-tab-btn {
  flex: none;
  min-height: 38px;
  padding: 0.4rem 0.85rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 0.86rem;
  font-weight: 500;
  color: var(--soft);
  white-space: nowrap;
  transition: border-color var(--fast) var(--ease), color var(--fast) var(--ease),
    transform var(--fast) var(--ease);
}

.filter-tab-btn.active {
  background: var(--accent-gradient);
  border-color: var(--accent);
  color: var(--on-accent);
}

/* ==========================================================================
   Lessons page: step-by-step selection
   ========================================================================== */
.flow-step {
  padding: 1.25rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--surface);
  transition: opacity 400ms var(--ease-out);
}

.flow-step.is-locked {
  opacity: 0.45;
  pointer-events: none;
}

.flow-heading {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  margin-bottom: 0.9rem;
}

.flow-number {
  display: grid;
  place-items: center;
  flex: none;
  width: 34px;
  height: 34px;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  font-size: 0.82rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

.flow-step:not(.is-locked) .flow-number {
  border-color: var(--accent);
  color: var(--accent-text);
}

.flow-heading .section-label {
  font-size: 0.7rem;
}

.flow-heading h2 {
  font-size: 1.15rem;
  font-weight: 700;
}

.flow-description,
.flow-hint {
  margin-bottom: 0.9rem;
  font-size: 0.9rem;
  color: var(--soft);
}

.choice-grid {
  display: grid;
  gap: 0.5rem;
}

.subject-choices {
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 260px), 1fr));
}

.grade-choices {
  grid-template-columns: repeat(6, minmax(0, 1fr));
}

.choice-card {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  min-height: 48px;
  padding: 0.75rem 0.9rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  text-align: left;
  transition: border-color var(--fast) var(--ease), background var(--fast) var(--ease),
    transform var(--fast) var(--ease);
}

.choice-card.compact {
  justify-content: center;
  padding: 0.5rem;
  font-size: 0.9rem;
  font-weight: 500;
  text-align: center;
}

.choice-info {
  display: grid;
  gap: 0.15rem;
  min-width: 0;
}

.choice-info strong {
  font-weight: 600;
}

.choice-info small {
  font-size: 0.82rem;
  color: var(--soft);
  line-height: 1.4;
}

.choice-card.selected {
  border-color: var(--accent);
  box-shadow: inset 0 0 0 1px var(--accent);
  background: var(--accent-soft);
}

.choice-card.compact.selected {
  background: var(--accent-gradient);
  color: var(--on-accent);
}

.topic-choices {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.topic-chip {
  min-height: 40px;
  padding: 0.45rem 0.8rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 0.88rem;
  font-weight: 500;
  text-align: left;
  transition: border-color var(--fast) var(--ease),
    transform var(--fast) var(--ease);
}

.topic-chip.selected {
  background: var(--accent-gradient);
  border-color: var(--accent);
  color: var(--on-accent);
}

/* ==========================================================================
   Lessons page: results
   ========================================================================== */
.results-panel {
  padding-top: 1.75rem;
}

.results-panel.is-locked {
  display: none;
}

.results-heading {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  justify-content: space-between;
  gap: 0.75rem 1rem;
  margin-bottom: 1rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}

.results-heading h2 {
  margin-top: 0.3rem;
  font-size: clamp(1.3rem, 4vw, 1.6rem);
  font-weight: 700;
}

.reset-button {
  min-height: 38px;
  padding: 0.4rem 0.8rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 0.86rem;
  color: var(--soft);
}

.lessons-grid {
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 340px), 1fr));
  align-items: start;
}

.lessons-empty {
  padding: 2rem 1rem;
  border: 1px dashed var(--border-strong);
  border-radius: var(--radius-lg);
  text-align: center;
  color: var(--soft);
}

/* ==========================================================================
   Lesson card
   ========================================================================== */
.lesson-card {
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--surface);
  scroll-margin-top: calc(var(--header-h) + 12px);
}

.lesson-card.highlighted {
  border-color: var(--accent);
  box-shadow: 0 0 0 1px var(--accent);
}

.lesson-media {
  position: relative;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background: #000;
  cursor: pointer;
}

.lesson-media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 600ms var(--ease-out);
}

.lesson-media iframe,
.lesson-media video {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: 0;
  background: #000;
  object-fit: contain;
}

.play-badge {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
}

.play-badge::before {
  content: "";
  width: 56px;
  height: 56px;
  border-radius: 14px;
  background: var(--media-ui);
  transition: background var(--fast) var(--ease), transform var(--medium) var(--ease-out);
}

.play-badge::after {
  content: "";
  position: absolute;
  margin-left: 4px;
  border-style: solid;
  border-width: 10px 0 10px 16px;
  border-color: transparent transparent transparent #fff;
}

.video-duration,
.lesson-completed-ribbon {
  position: absolute;
  padding: 0.15rem 0.45rem;
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 600;
  line-height: 1.5;
  pointer-events: none;
}

.video-duration {
  right: 0.6rem;
  bottom: 0.6rem;
  background: var(--media-ui);
  color: #fff;
  font-variant-numeric: tabular-nums;
}

.lesson-completed-ribbon {
  left: 0.6rem;
  top: 0.6rem;
  background: var(--success);
  color: var(--bg);
}

.lesson-card-top-actions {
  position: absolute;
  top: 0.5rem;
  right: 0.5rem;
  z-index: 2;
  display: flex;
  gap: 0.35rem;
}

.card-icon-action {
  display: grid;
  place-items: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius);
  background: var(--media-ui);
  color: #fff;
  font-size: 1rem;
  line-height: 1;
}

.bookmark-action-btn.active {
  color: #fbbf24;
}

.lesson-media.is-pending {
  cursor: default;
  background: var(--surface-subtle);
}

.pending-media {
  position: absolute;
  inset: 0;
  display: grid;
  place-content: center;
  gap: 0.2rem;
  padding: 1rem;
  text-align: center;
}

.pending-icon {
  display: none;
}

.pending-text {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--faint);
}

.pending-topic {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--soft);
}

.lesson-body {
  display: grid;
  gap: 0.75rem;
  padding: 1.1rem 1.1rem 1.25rem;
}

.lesson-badge-wrap {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.25rem 0.6rem;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--faint);
}

.lesson-badge-wrap > span + span::before {
  content: "·";
  margin-right: 0.6rem;
}

.lesson-subject {
  color: var(--accent-text);
}

/* the topic repeats the card title, so it is left out of the label row */
.lesson-topic-badge {
  display: none;
}

.lesson-card h3 {
  font-size: 1.12rem;
  font-weight: 700;
  line-height: 1.3;
}

.lesson-desc-text {
  font-size: 0.92rem;
  color: var(--soft);
}

.lesson-takeaway {
  padding: 0.7rem 0.85rem;
  border: 1px solid var(--accent-border);
  border-radius: var(--radius);
  background: var(--accent-soft);
  font-size: 0.9rem;
  line-height: 1.5;
}

.takeaway-icon {
  display: none;
}

.takeaway-text strong {
  display: block;
  margin-bottom: 0.2rem;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-text);
}

/* Quiz */
.quiz-lock-status {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  padding-top: 0.75rem;
  border-top: 1px solid var(--border);
}

.quiz-lock-badge {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  min-width: 0;
  font-size: 0.86rem;
  color: var(--soft);
}

/* the status icon is only shown once the lesson is completed (✓) */
.quiz-lock-icon {
  display: none;
}

.is-completed .quiz-lock-icon {
  display: inline;
  flex: none;
  font-weight: 700;
  color: var(--success);
}

.quiz-unlock-btn {
  flex: none;
  min-height: 40px;
  padding: 0.4rem 0.8rem;
  border: 1px solid var(--accent-border);
  border-radius: var(--radius);
  background: var(--accent-soft);
  color: var(--accent-text);
  font-size: 0.86rem;
  font-weight: 600;
  white-space: nowrap;
}





.quiz-q-title {
  margin-bottom: 0.5rem;
  font-size: 0.95rem;
  font-weight: 600;
  line-height: 1.45;
}

.q-num {
  color: var(--faint);
}

.quiz-options {
  display: grid;
  gap: 0.4rem;
}

.quiz-option-label {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  min-height: 44px;
  padding: 0.55rem 0.8rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 0.92rem;
  line-height: 1.4;
  cursor: pointer;
  transition: border-color var(--fast) var(--ease), background var(--fast) var(--ease),
    transform var(--fast) var(--ease);
}

.quiz-option-label input {
  flex: none;
  width: 18px;
  height: 18px;
  accent-color: var(--accent);
}

.quiz-option-label.checked {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.quiz-option-label.is-correct {
  border-color: var(--success);
  background: var(--success-soft);
}

.quiz-option-label.is-wrong {
  border-color: var(--danger);
  background: var(--danger-soft);
}








/* Interactive tasks: scales, protractor, number line, grid… (js/tasks.js) */
.task {
  display: grid;
  gap: 0.6rem;
  padding: 0.75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--fig-paper);
  transition: border-color var(--fast) var(--ease), box-shadow var(--fast) var(--ease);
}

.is-correct > .task {
  border-color: var(--success);
  box-shadow: 0 0 0 1px var(--success);
}

.is-wrong > .task {
  border-color: var(--danger);
  box-shadow: 0 0 0 1px var(--danger);
}

.task-fig {
  display: block;
  width: 100%;
  max-width: 400px;
  height: auto;
  margin-inline: auto;
  overflow: visible;
  font-family: var(--font-body);
  user-select: none;
  -webkit-user-select: none;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
}

.task-plane .task-fig,
.task-line .task-fig {
  max-width: 320px;
}

.task-pick .task-fig {
  max-width: 280px;
}

.task-fig:focus-visible,
.task-fig .f-pick:focus-visible {
  outline: none;
}

.task-fig:focus-visible {
  border-radius: var(--radius-sm);
  box-shadow: 0 0 0 2px var(--accent);
}

.is-tappable,
.f-pick,
.f-handle {
  cursor: pointer;
}

.f-handle {
  cursor: grab;
  touch-action: none;
}

/* shapes */
.f-ink { fill: var(--ink); }
.f-paper { fill: var(--fig-paper); }
.f-axis { stroke: var(--ink); stroke-width: 2; stroke-linecap: round; }
.f-grid { stroke: var(--fig-grid); stroke-width: 1; }
.f-tick { stroke: var(--ink); stroke-width: 1.6; stroke-linecap: round; }
.f-string { stroke: var(--soft); stroke-width: 1.6; fill: none; }
.f-hit { fill: transparent; }
.f-hit-line { stroke: transparent; stroke-width: 22; stroke-linecap: round; fill: none; }

.f-label {
  fill: var(--soft);
  font-size: 10px;
  font-weight: 500;
}

.f-small { font-size: 9px; }
.task-numberline .f-label { font-size: 12px; }
.f-zero { fill: var(--ink); font-weight: 700; }
.f-value { fill: var(--ink); font-weight: 600; }
.f-axis-name { fill: var(--ink); font-style: italic; font-size: 11px; }

.f-point-name {
  fill: var(--ink);
  font-size: 11px;
  font-weight: 700;
  font-style: italic;
}

.f-readout,
.f-wedge-text,
.f-knob-text {
  font-family: var(--font-display);
  font-weight: 700;
  text-anchor: middle;
}

/* scales */
.f-box { fill: var(--fig-mustard); stroke: var(--fig-on-color); stroke-opacity: 0.25; }
.f-box-text { fill: var(--fig-on-color); font-size: 15px; font-weight: 700; font-style: italic; }
.f-weight { fill: var(--fig-teal); }
.f-weight-ring { fill: none; stroke: var(--fig-teal); stroke-width: 2.4; }
.f-weight-text { fill: #ffffff; font-size: 12px; font-weight: 700; }
.f-pan { fill: var(--ink); }
.f-needle { fill: var(--fig-red); transition: fill var(--medium) var(--ease); }
.is-level .f-needle { fill: var(--success); }

/* protractor */
.f-protractor { fill: var(--accent-soft); stroke: var(--accent-border); stroke-width: 1.2; }
.f-ray { stroke: var(--ink); stroke-width: 3; stroke-linecap: round; }
.f-ray-move { stroke: var(--accent); }
.f-wedge { fill: var(--fig-mustard-soft); stroke: var(--fig-mustard); stroke-width: 1.6; }
.f-readout { fill: var(--ink); font-size: 13px; }
.f-knob { fill: var(--accent); stroke: var(--surface); stroke-width: 2.5; }
.f-knob-text { fill: var(--on-accent); font-size: 9px; }
.f-handle:active .f-knob { cursor: grabbing; }

/* tap targets: number line ticks and parts of a figure */
.f-mark { fill: transparent; stroke: transparent; stroke-width: 2.5; }
.f-pick.is-on .f-mark { fill: var(--accent); }
.f-pick.is-answer .f-mark { stroke: var(--success); }
.f-pick.is-miss .f-mark { fill: var(--danger); }
.f-pick:focus-visible .f-mark,
.f-pick:focus-visible .f-part-shape { stroke: var(--accent); }

.f-disk { fill: var(--fig-teal-soft); stroke: var(--ink); stroke-width: 3; }
.f-part-line .f-part-shape { fill: none; stroke: var(--ink); stroke-width: 3; stroke-linecap: round; transition: stroke var(--fast) var(--ease), stroke-width var(--fast) var(--ease); }
.f-part-line.is-on .f-part-shape { stroke: var(--accent); stroke-width: 5; }
.f-part-line.is-answer .f-part-shape { stroke: var(--success); stroke-width: 5; }
.f-part-line.is-miss .f-part-shape { stroke: var(--danger); }

.f-part-area .f-part-shape { fill: var(--surface); stroke: var(--ink); stroke-width: 2.5; transition: fill var(--fast) var(--ease); }
.f-part-area.is-on .f-part-shape { fill: var(--accent-tint); }
.f-part-area.is-answer .f-part-shape { fill: var(--fig-ok-soft); }
.f-part-area.is-miss .f-part-shape { fill: var(--danger-soft); }
.f-area-text { fill: var(--ink); font-size: 16px; font-weight: 700; text-anchor: middle; opacity: 0; transition: opacity var(--medium) var(--ease); }
.show-areas .f-area-text { opacity: 1; }
.f-side { font-size: 14px; font-weight: 700; font-style: italic; text-anchor: middle; }
.f-side-a { fill: var(--fig-teal); }
.f-side-b { fill: #c98a12; }
:root[data-theme="dark"] .f-side-b { fill: var(--fig-mustard); }

/* coordinate plane */
.f-dot { fill: var(--accent); stroke: var(--surface); stroke-width: 2; }
.f-point .f-dot { fill: var(--accent); stroke: var(--surface); stroke-width: 2; }
.f-ghost-dot { fill: none; stroke: var(--success); stroke-width: 2.5; }
.f-guide { fill: none; stroke: var(--success); stroke-width: 1.6; stroke-dasharray: 4 3; }
.f-graph { stroke: var(--accent); stroke-width: 3; stroke-linecap: round; }
.f-target-dot { fill: var(--surface); stroke: var(--fig-red); stroke-width: 3; transition: fill var(--fast) var(--ease), stroke var(--fast) var(--ease); }
.f-target.is-hit .f-target-dot { fill: var(--success); stroke: var(--success); }
.f-target-text { fill: var(--ink); font-size: 9px; font-weight: 600; paint-order: stroke; stroke: var(--fig-paper); stroke-width: 3; }

/* bars and the mean line */
.f-bar { fill: var(--fig-teal); }
.f-over { fill: var(--fig-paper); fill-opacity: 0.55; }
.f-under { fill: var(--fig-teal-soft); stroke: var(--fig-teal); stroke-width: 1.2; stroke-dasharray: 3 2; }
.f-level-line { stroke: var(--fig-mustard); stroke-width: 3; stroke-dasharray: 7 4; stroke-linecap: round; }

/* triangle corners on a straight line */
.f-tri { fill: none; stroke: var(--ink); stroke-width: 2.5; stroke-linejoin: round; }
.f-w-a { fill: var(--fig-teal); }
.f-w-b { fill: var(--fig-mustard); }
.f-w-c { fill: var(--fig-red); }
.f-big { stroke: var(--fig-paper); stroke-width: 1.5; }
.f-w-c.is-over { fill-opacity: 0.55; stroke: var(--fig-red); stroke-dasharray: 4 3; }
.f-wedge-text { fill: var(--fig-on-color); font-size: 11px; }

/* controls under the drawing */
.task-controls {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.5rem 0.9rem;
}

.task-step {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
}

/* phones: a long label («Закрашено», «Скидка») goes above the field so the unit stays inside the card */
@media (max-width: 480px) {
  .task-number {
    flex-wrap: wrap;
    justify-content: center;
  }

  .task-number .task-step-name {
    flex-basis: 100%;
    text-align: center;
  }
}

.task-step-name {
  font-family: var(--font-display);
  font-size: 0.85rem;
  font-weight: 600;
  font-style: italic;
  color: var(--soft);
}

.task-step-btn {
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--accent-text);
  font-size: 1.25rem;
  font-weight: 600;
  line-height: 1;
  transition: background var(--fast) var(--ease), border-color var(--fast) var(--ease), transform var(--fast) var(--ease);
}

/* hover tints only where there is a real hover, so a tap on a phone doesn't leave one behind */
@media (hover: hover) {
  .task-step-btn:hover:not(:disabled) {
    border-color: var(--accent);
    background: var(--accent-soft);
  }

  .f-pick:not(.is-on):hover .f-mark { fill: var(--accent-tint); }
  .f-part-line:not(.is-on):hover .f-part-shape { stroke: var(--accent-text); }
  .f-part-area:not(.is-on):hover .f-part-shape { fill: var(--accent-soft); }
}

.task-step-btn:active:not(:disabled) {
  transform: scale(0.92);
}

.task-step-btn:disabled {
  opacity: 0.4;
  cursor: default;
}

.task-step-out {
  min-width: 2.6ch;
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  text-align: center;
}

.task-slider {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  width: 100%;
  max-width: 400px;
}

.task-slider .task-step-name {
  flex: none;
  font-style: normal;
}

.task-range {
  flex: 1;
  min-width: 0;
  height: 44px;
  accent-color: var(--accent);
}

.task-formula {
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 700;
  text-align: center;
  color: var(--accent-text);
}

.task-answer {
  font-size: 0.86rem;
  font-weight: 600;
  line-height: 1.45;
  text-align: center;
  color: var(--success);
}

.task.is-locked .task-fig,
.task.is-locked .task-controls {
  pointer-events: none;
}

.task.is-locked .task-controls {
  opacity: 0.6;
}

/* ==========================================================================
   Lessons page: the steps box — one step at a time, swapped in place
   ========================================================================== */
.flow-box {
  overflow: hidden;
  padding: 1.25rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--surface);
  scroll-margin-top: calc(var(--header-h) + 12px);
}

.flow-box .flow-progress {
  margin: -0.35rem 0 1.1rem;
  padding-bottom: 0.85rem;
  border-bottom: 1px solid var(--border);
}

.flow-box > .flow-step,
.flow-box > .flow-step.is-locked {
  display: none;
  padding: 0;
  border: 0;
  background: none;
  opacity: 1;
  pointer-events: auto;
}

.flow-box[data-pane="1"] > [data-pane-id="1"],
.flow-box[data-pane="2"] > [data-pane-id="2"],
.flow-box[data-pane="3"] > [data-pane-id="3"] {
  display: block;
}

.progress-step {
  min-height: 40px;
  padding: 0.3rem 0.45rem;
  border-radius: var(--radius);
  color: inherit;
  font: inherit;
}

.progress-step:disabled {
  cursor: default;
  opacity: 0.55;
}

.flow-back {
  display: grid;
  place-items: center;
  flex: none;
  width: 40px;
  height: 40px;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  font-size: 1.1rem;
  color: var(--accent-text);
  transition: background var(--fast) var(--ease), transform var(--fast) var(--ease);
}

/* ==========================================================================
   Quiz dialog: one question at a time
   ========================================================================== */
.modal.quiz-modal {
  display: flex;
  flex-direction: column;
  width: min(580px, 100%);
  padding: 0;
  overflow: hidden;
}

.quiz-modal:focus {
  outline: none;
}

.qm-head {
  padding: 1.4rem 1.5rem 0.6rem;
}

.quiz-modal .qm-title {
  margin: 0.3rem 2.75rem 0.9rem 0;
  font-size: 1.12rem;
  line-height: 1.35;
  text-wrap: balance;
}

.qm-progress {
  display: flex;
  gap: 0.35rem;
}

.qm-seg {
  flex: 1;
  height: 6px;
  border-radius: 3px;
  background: var(--border);
  transition: background var(--medium) var(--ease);
}

.qm-seg.is-current { background: var(--accent); }
.qm-seg.is-right { background: var(--success); }
.qm-seg.is-wrong { background: var(--danger); }

.qm-count {
  margin-top: 0.65rem;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--faint);
}

.qm-scroll {
  display: grid;
  flex: 1 1 auto;
  align-content: start;
  gap: 0.9rem;
  min-height: 0;
  overflow-y: auto;
  overscroll-behavior: contain;
  padding: 0.35rem 1.5rem 1.1rem;
}

.qm-body .quiz-q-title {
  margin-bottom: 0.75rem;
  font-size: 1rem;
}

.qm-feedback {
  padding: 0.75rem 0.9rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 0.9rem;
  line-height: 1.5;
}

.qm-feedback.success { border-color: var(--success-border); background: var(--success-soft); color: var(--success); }
.qm-feedback.error { border-color: var(--danger-border); background: var(--danger-soft); color: var(--danger); }
.qm-feedback.info { border-color: var(--accent-border); background: var(--accent-soft); color: var(--accent-text); }

.qm-foot {
  display: flex;
  justify-content: flex-end;
  padding: 0.85rem 1.5rem 1.2rem;
  border-top: 1px solid var(--border);
}

.qm-main {
  min-width: 11rem;
}

.qm-result {
  padding: 1.75rem 0 0.75rem;
  text-align: center;
}

.qm-score {
  font-family: var(--font-display);
  font-weight: 600;
  color: var(--soft);
}

.qm-score span {
  display: block;
  font-size: 3.6rem;
  font-weight: 700;
  line-height: 1.1;
  color: var(--accent-text);
}

.qm-result.is-all .qm-score span {
  color: var(--success);
}

.qm-result-text {
  max-width: 34ch;
  margin: 0.6rem auto 0;
  color: var(--soft);
  text-wrap: balance;
}

/* ==========================================================================
   Drawings of the newer tasks
   ========================================================================== */
.f-jump { fill: none; stroke: var(--accent); stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
.f-start { fill: var(--fig-mustard); }
.f-start-text { fill: var(--ink); font-weight: 700; }
.f-quadrant { fill: var(--accent-soft); fill-opacity: 0.7; }
.f-graph-given { stroke: var(--soft); stroke-width: 2.4; stroke-dasharray: 7 5; }
.f-graph-answer { stroke: var(--success); stroke-dasharray: 6 4; }
.f-shape { fill: var(--accent-soft); fill-opacity: 0.6; stroke: var(--accent); stroke-width: 2; stroke-dasharray: 5 4; }
.f-column { stroke: var(--accent); stroke-opacity: 0.16; stroke-width: 12; }

.f-overlay,
.f-decor,
.f-wedge-num { pointer-events: none; }
.f-decor-line { fill: none; stroke: var(--ink); stroke-width: 2.6; stroke-linecap: round; pointer-events: none; }
.f-thin { stroke-width: 1.6; }
.f-dashed { stroke-dasharray: 4 3; }
.f-given-wedge { fill: var(--fig-mustard); }
.f-wedge-num { fill: var(--ink); font-size: 13px; font-weight: 700; text-anchor: middle; }

.f-part-bar .f-part-shape { fill: var(--fig-teal); transition: fill var(--fast) var(--ease); }
.f-part-bar.is-on .f-part-shape { fill: var(--accent); }
.f-part-bar.is-answer .f-part-shape { fill: var(--success); }
.f-part-bar.is-miss .f-part-shape { fill: var(--danger); }
.f-part-bar .f-value { pointer-events: none; }

.task-pick .task-fig.fig-righttri {
  max-width: 300px;
}

.task-enter .task-fig.fig-righttri,
.task-enter .task-fig.fig-pifsquares,
.task-enter .task-fig.fig-room {
  max-width: 300px;
}

.task-pick .task-fig.fig-lines,
.task-pick .task-fig.fig-solids,
.task-pick .task-fig.fig-bars,
.task-pick .task-fig.fig-dice,
.task-pick .task-fig.fig-triangles {
  max-width: 400px;
}

/* right triangles, squares on the sides, the room, number cards, the parabola */
.f-stick-hyp { stroke: var(--fig-red); }
.f-sq-teal { fill: var(--fig-teal); stroke: var(--ink); stroke-width: 1.5; }
.f-sq-mustard { fill: var(--fig-mustard); stroke: var(--ink); stroke-width: 1.5; }
.f-sq-red { fill: var(--fig-red); stroke: var(--ink); stroke-width: 1.5; }
.f-sq-teal + .f-cube-lines,
.f-sq-mustard + .f-cube-lines,
.f-sq-red + .f-cube-lines { stroke: #ffffff; stroke-opacity: 0.45; }
.f-big-label { font-size: 18px; font-weight: 700; }
.f-room { fill: var(--fig-teal-soft); stroke: var(--ink); stroke-width: 3; }
.f-card { fill: var(--fig-teal); }
.f-card-ask { fill: var(--fig-paper); stroke: var(--fig-red); stroke-width: 2.5; stroke-dasharray: 5 4; }
.f-card-text { fill: #ffffff; font-family: var(--font-display); font-size: 18px; font-weight: 700; text-anchor: middle; }
.f-card-ask + .f-card-text { fill: var(--fig-red); }
.f-dots { fill: var(--ink); font-size: 22px; font-weight: 700; }
.f-hop { fill: none; stroke: var(--fig-mustard); stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
.f-hop-text { fill: var(--ink); font-weight: 700; }
.f-root { fill: var(--fig-red); stroke: var(--surface); stroke-width: 2.5; }

/* inequality ray, graphs given on the grid, balls in a box, an equation system */
.f-ray-band { stroke: var(--accent); stroke-width: 7; stroke-linecap: round; stroke-opacity: 0.75; }
.f-ray-head { fill: var(--accent); }
.f-ray-dot { fill: var(--fig-paper); stroke: var(--accent); stroke-width: 3.5; }
.f-ray-dot.is-closed { fill: var(--accent); }
.f-graph-given.f-graph-0 { stroke: var(--fig-teal); stroke-dasharray: none; }
.f-graph-given.f-graph-1 { stroke: var(--fig-mustard); stroke-dasharray: none; }
.f-graph-given.f-curve { stroke: var(--accent); stroke-dasharray: none; }
.f-box-frame { fill: var(--fig-paper); stroke: var(--ink); stroke-width: 2.5; }
.f-ball-red { fill: var(--fig-red); }
.f-ball-blue { fill: var(--accent); }
.f-part-ball .f-part-shape { stroke: transparent; stroke-width: 4; transition: stroke var(--fast) var(--ease); }
.f-part-ball.is-on .f-part-shape { stroke: var(--ink); stroke-width: 5; }
.f-part-ball.is-answer .f-part-shape { stroke: var(--success); stroke-width: 6; }
.f-part-ball.is-miss .f-part-shape { stroke: var(--danger); stroke-width: 6; stroke-dasharray: 4 3; }
.f-brace { fill: var(--ink); font-size: 96px; font-weight: 300; }
.f-eq-text { fill: var(--ink); font-family: var(--font-display); font-size: 28px; font-weight: 700; }

.task-toggle {
  display: inline-flex;
  overflow: hidden;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
}

.task-toggle button {
  min-height: 44px;
  padding: 0 0.85rem;
  background: var(--surface);
  color: var(--ink);
  font-size: 0.88rem;
  font-weight: 600;
  transition: background var(--fast) var(--ease), color var(--fast) var(--ease);
}

.task-toggle button + button {
  border-left: 1px solid var(--border-strong);
}

.task-toggle button.is-on {
  background: var(--accent);
  color: var(--on-accent);
}

.task-pick .task-fig.fig-parabs,
.task-pick .task-fig.fig-balls,
.task-enter .task-fig.fig-balls {
  max-width: 400px;
}

.task-enter .task-fig.fig-system {
  max-width: 320px;
}

/* Russian-language tasks: words to tap, punctuation gaps, answer cards, sorting chips */
.tok-row,
.punct-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.35rem 0.4rem;
  padding: 0.4rem 0;
  font-family: var(--font-display);
  font-size: 1.12rem;
  font-weight: 600;
}

.tok {
  min-height: 46px;
  padding: 0 0.7rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  font: inherit;
  transition: background var(--fast) var(--ease), border-color var(--fast) var(--ease), color var(--fast) var(--ease);
}

.tok-row.is-tiles .tok {
  min-width: 52px;
  min-height: 62px;
  padding: 0 0.5rem;
  font-size: 1.6rem;
}

.tok.is-on { border-color: var(--accent); background: var(--accent-soft); color: var(--accent-text); }
.tok.is-answer { border-color: var(--success); background: var(--success-soft); color: var(--success); }
.tok.is-miss { border-color: var(--danger); background: var(--danger-soft); color: var(--danger); }

.punct-word { padding: 0.2rem 0; }

.punct-gap {
  display: inline-grid;
  place-items: center;
  min-width: 30px;
  padding: 0 4px;
  min-height: 46px;
  white-space: nowrap;
  border: 1.5px dashed var(--border-strong);
  border-radius: 8px;
  background: transparent;
  color: var(--ink);
  font: inherit;
  font-size: 1.25rem;
  transition: background var(--fast) var(--ease), border-color var(--fast) var(--ease);
}

.punct-gap.is-on { border-style: solid; border-color: var(--accent); background: var(--accent-soft); color: var(--accent-text); }
.punct-gap.is-answer { border-style: solid; border-color: var(--success); background: var(--success-soft); color: var(--success); }
.punct-gap.is-miss { border-style: solid; border-color: var(--danger); background: var(--danger-soft); color: var(--danger); }
.punct-gap.is-missing:not(.is-on) { border-color: var(--success); }

.choice-list { display: grid; gap: 0.45rem; }

.choice-opt {
  min-height: 48px;
  padding: 0.5rem 0.9rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  font-size: 0.95rem;
  font-weight: 500;
  line-height: 1.4;
  text-align: left;
  transition: background var(--fast) var(--ease), border-color var(--fast) var(--ease);
}

.choice-opt.is-on { border-color: var(--accent); background: var(--accent-soft); }
.choice-opt.is-answer { border-color: var(--success); background: var(--success-soft); color: var(--success); }
.choice-opt.is-miss { border-color: var(--danger); background: var(--danger-soft); color: var(--danger); }

/* pick a mark or a group first, then tap where it goes */
.task-palette {
  justify-self: center;
  flex-wrap: wrap;
  max-width: 100%;
}

.task-palette button { min-width: 52px; }
.pal-mark { font-family: var(--font-display); font-size: 1.3rem; font-weight: 700; line-height: 1; }
/* sorting: drag words from the pool into the group boxes */
.sort-board { display: grid; gap: 0.7rem; touch-action: pan-y; }
.sort-pool {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-content: flex-start;
  gap: 0.45rem;
  min-height: 58px;
  padding: 0.5rem;
  border: 2px dashed var(--border-strong);
  border-radius: var(--radius);
  transition: border-color var(--fast) var(--ease), background var(--fast) var(--ease);
}
.sort-board.is-sorted .sort-pool { border-color: transparent; min-height: 0; padding: 0; }
.sort-zones { display: grid; grid-template-columns: repeat(var(--n, 2), minmax(0, 1fr)); gap: 0.55rem; }
.sort-zone {
  display: grid;
  grid-template-rows: auto 1fr;
  min-height: 132px;
  border: 2px dashed var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  transition: border-color var(--fast) var(--ease), background var(--fast) var(--ease), transform var(--fast) var(--ease);
}
.sort-zone.b0 { border-color: var(--fig-teal); }
.sort-zone.b1 { border-color: var(--fig-mustard); }
.sort-zone-head {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.45rem 0.6rem;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--soft);
  line-height: 1.25;
}
.sort-zone-head i {
  display: inline-grid;
  place-items: center;
  flex: none;
  min-width: 26px;
  height: 24px;
  padding: 0 5px;
  border-radius: 6px;
  font-family: var(--font-display);
  font-size: 0.75rem;
  font-style: normal;
  color: #ffffff;
}
.sort-zone.b0 .sort-zone-head i { background: var(--fig-teal); }
.sort-zone.b1 .sort-zone-head i { background: var(--fig-mustard); color: var(--fig-on-color); }
.sort-zone-body { display: flex; flex-wrap: wrap; align-content: flex-start; gap: 0.4rem; padding: 0 0.45rem 0.5rem; }
.sort-zone.is-over, .sort-pool.is-over { border-style: solid; transform: scale(1.02); }
.sort-zone.b0.is-over { background: var(--fig-teal-soft); }
.sort-zone.b1.is-over { background: var(--fig-mustard-soft); }
.sort-pool.is-over { border-color: var(--accent); background: var(--accent-soft); }

.sort-chip {
  position: relative;
  min-height: 44px;
  padding: 0.35rem 0.75rem;
  border: 1.5px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  font-family: var(--font-display);
  font-size: 0.95rem;
  font-weight: 600;
  line-height: 1.25;
  text-align: center;
  cursor: grab;
  touch-action: none;
  user-select: none;
  -webkit-user-select: none;
  box-shadow: 0 2px 0 var(--border-strong);
  transition: border-color var(--fast) var(--ease), background var(--fast) var(--ease), box-shadow var(--fast) var(--ease);
}
/* inside a narrow group box a long word shrinks a little and may break rather than poke out of the box */
.sort-zone-body .sort-chip { max-width: 100%; padding-inline: 0.55rem; font-size: 0.88rem; overflow-wrap: anywhere; }
.sort-chip[data-b="0"] { border-color: var(--fig-teal); background: var(--fig-teal-soft); box-shadow: 0 2px 0 var(--fig-teal); }
.sort-chip[data-b="1"] { border-color: var(--fig-mustard); background: var(--fig-mustard-soft); box-shadow: 0 2px 0 var(--fig-mustard); }
.sort-chip.is-dragging {
  z-index: 20;
  cursor: grabbing;
  box-shadow: 0 14px 28px -10px rgba(0, 0, 0, 0.35);
  transition: none;
}
.sort-chip.is-answer { border-color: var(--success); }
.sort-chip.is-miss { border-color: var(--danger); border-style: dashed; }
.task.is-locked .sort-chip { cursor: default; }

.f-letter { fill: var(--fig-teal); }
.f-letter-text { fill: #ffffff; font-family: var(--font-display); font-size: 30px; font-weight: 700; text-anchor: middle; }

/* bar model */
.f-strip rect { stroke: var(--fig-paper); stroke-width: 2; transition: fill var(--fast) var(--ease); }
.f-strip-n rect { fill: var(--fig-teal); }
.f-strip-x rect { fill: var(--fig-mustard); }
.f-strip-x rect.is-unknown { fill: var(--fig-mustard-soft); stroke: var(--fig-mustard); stroke-dasharray: 5 4; }
.f-strip-text { fill: #ffffff; font-size: 13px; font-weight: 700; text-anchor: middle; pointer-events: none; }
.f-strip-x .f-strip-text { fill: var(--fig-on-color); font-style: italic; }
.f-strip-end { stroke: var(--soft); stroke-width: 1.5; stroke-dasharray: 4 4; }
.is-equal .f-strip-end { stroke: var(--success); stroke-width: 3; stroke-dasharray: none; }

/* rectangle on squared paper */
.f-rect { fill: var(--accent-tint); fill-opacity: 0.85; stroke: var(--accent); stroke-width: 2.5; }
.f-side-c { fill: var(--fig-red); }

/* box of cubes and the 101² square */
.f-cube-top { fill: var(--fig-mustard-soft); stroke: var(--ink); stroke-width: 1.8; stroke-linejoin: round; }
.f-cube-left { fill: var(--fig-teal-soft); stroke: var(--ink); stroke-width: 1.8; stroke-linejoin: round; }
.f-cube-right { fill: var(--fig-teal-mid); stroke: var(--ink); stroke-width: 1.8; stroke-linejoin: round; }
.f-cube-lines { fill: none; stroke: var(--ink); stroke-width: 1; stroke-opacity: 0.5; }
.f-sq-a { fill: var(--fig-teal-soft); stroke: var(--ink); stroke-width: 2; }
.f-cell { fill: var(--fig-paper); stroke: var(--ink); stroke-opacity: 0.35; stroke-width: 1; }
.f-cell.is-filled { fill: var(--fig-teal); stroke-opacity: 0.6; }
.f-cross-line { stroke: var(--fig-red); stroke-width: 2.5; stroke-dasharray: 6 5; fill: none; }
.f-frac-bar { stroke: var(--ink); stroke-width: 3; }
.f-prop-term { fill: var(--ink); font-family: var(--font-display); font-size: 30px; font-weight: 700; }
.f-prop-term.is-x { fill: var(--fig-red); }
.f-prime { fill: var(--fig-teal); }
.f-prime-text { fill: #ffffff; font-family: var(--font-display); font-size: 20px; font-weight: 700; text-anchor: middle; }
.f-pie-slice { fill: var(--fig-red); stroke: var(--ink); stroke-width: 1.6; pointer-events: none; }
.f-sq-ab { fill: var(--fig-red-soft); stroke: var(--ink); stroke-width: 2; }
.f-sq-b { fill: var(--fig-mustard); stroke: var(--ink); stroke-width: 2; }
.f-area-label { fill: var(--ink); font-size: 12px; font-weight: 600; text-anchor: middle; }

/* rolling wheel */
.f-wheel { fill: var(--fig-teal-soft); stroke: var(--ink); stroke-width: 2.5; }
.f-spoke { stroke: var(--fig-red); stroke-width: 2; }
.f-rim-mark { fill: var(--fig-red); stroke: var(--surface); stroke-width: 2; }
.f-trace { fill: none; stroke: var(--fig-red); stroke-width: 1.6; stroke-dasharray: 3 3; }
.f-roll-flag-line { stroke: var(--accent); stroke-width: 2; }

/* sticks */
.f-stick { stroke-width: 7; stroke-linecap: round; transition: opacity var(--fast) var(--ease); }
.f-stick-a { stroke: var(--fig-teal); }
.f-stick-b { stroke: var(--fig-mustard); }
.f-stick-c { stroke: var(--ink); }
.f-tri-fill { fill: var(--fig-teal-soft); }
.f-note { font-size: 12px; font-weight: 700; fill: var(--success); }
.is-broken .f-note { fill: var(--danger); }
.is-broken .f-stick-a,
.is-broken .f-stick-b { opacity: 0.75; }

/* number fields under a drawing */
.task-entry {
  width: 7ch;
  min-height: 44px;
  padding: 0 0.5rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  text-align: center;
}

.task-entry:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
}

.task-unit {
  font-weight: 600;
  color: var(--soft);
}

.task-hint {
  font-size: 0.82rem;
  text-align: center;
  color: var(--faint);
}

/* cards to put in order */
.order-board {
  display: grid;
  gap: 0.8rem;
}

.order-slots,
.order-pool {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.45rem;
}

.order-slot,
.order-card {
  display: grid;
  place-items: center;
  width: 50px;
  height: 54px;
  border-radius: var(--radius);
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 700;
}

.order-slot {
  border: 2px dashed var(--border-strong);
}

.order-card {
  border: 1px solid var(--border-strong);
  background: var(--surface);
  color: var(--ink);
}

.order-card.is-placed {
  border-color: transparent;
  background: var(--fig-teal);
  color: #ffffff;
}

.order-card.is-gone {
  visibility: hidden;
}

/* phrases instead of numbers: full-width rows, one under another */
.order-board.is-text .order-slots,
.order-board.is-text .order-pool {
  flex-direction: column;
  align-items: stretch;
}

.order-board.is-text .order-slot,
.order-board.is-text .order-card {
  width: auto;
  min-height: 46px;
  height: auto;
  padding: 0.45rem 0.9rem;
  font-family: var(--font-body);
  font-size: 1rem;
  font-weight: 600;
  text-align: center;
}

.order-board.is-text .order-card.is-gone {
  display: none;
}

.order-slot.is-middle,
.order-card.is-middle {
  box-shadow: 0 0 0 3px var(--fig-mustard);
}

/* expressions with signs and terms to tap */
.task-expr {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.3rem;
  padding: 0.6rem 0;
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 700;
}

.sign-btn {
  width: 40px;
  height: 44px;
  border: 1px solid var(--accent-border);
  border-radius: var(--radius);
  background: var(--accent-soft);
  color: var(--accent-text);
  font: inherit;
}

.sign-btn.is-minus {
  border-color: var(--fig-mustard);
  background: var(--fig-mustard-soft);
  color: var(--ink);
}

.term-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  min-height: 46px;
  padding: 0 0.75rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  font: inherit;
}

.term-btn.is-x {
  border-color: var(--fig-mustard);
  background: var(--fig-mustard-soft);
}

.term-sign {
  color: var(--soft);
}

.expr-eq {
  padding: 0 0.35rem;
  color: var(--soft);
}

/* pairs to match */
.match-board {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.6rem;
}

.match-col {
  display: grid;
  align-content: start;
  gap: 0.45rem;
}

.match-btn {
  min-height: 50px;
  padding: 0.5rem 0.6rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  font-family: var(--font-display);
  font-size: 0.9rem;
  font-weight: 600;
}

.match-btn.is-active { border-color: var(--accent); box-shadow: 0 0 0 2px var(--accent); }
.match-btn[data-pair="1"] { border-color: var(--fig-teal); background: var(--fig-teal-soft); }
.match-btn[data-pair="2"] { border-color: var(--fig-mustard); background: var(--fig-mustard-soft); }
.match-btn[data-pair="3"] { border-color: var(--accent); background: var(--accent-tint); }

/* table of values */
.value-table {
  margin: 0 auto;
  border-collapse: collapse;
  font-family: var(--font-display);
  font-variant-numeric: tabular-nums;
}

.value-table th,
.value-table td {
  min-width: 2.7rem;
  padding: 0.4rem 0.6rem;
  border: 1px solid var(--border-strong);
  text-align: center;
}

.value-table th {
  font-style: italic;
  color: var(--soft);
}

.value-table td.is-active {
  background: var(--accent-soft);
}

/* motion: steps slide in the box (JS), questions and results slide in the dialog */
.anim .qm-body > * {
  animation: pane-in 0.38s var(--ease-out) backwards;
}

.anim .qm-feedback:not([hidden]) {
  animation: rise 0.35s var(--ease-out) backwards;
}

.anim .order-card.is-placed,
.anim .term-btn.is-moved {
  animation: select-pop 0.35s var(--spring);
}

@keyframes pane-in {
  from {
    opacity: 0;
    transform: translateX(24px);
  }
}

@media (max-width: 860px) {
  .modal.quiz-modal {
    max-height: 94vh;
    max-height: 94dvh;
    padding: 0;
  }

  .quiz-modal .sheet-handle {
    margin: 0.6rem auto 0;
  }

  .qm-head {
    padding: 0.9rem 1.1rem 0.5rem;
  }

  .qm-scroll {
    padding: 0.3rem 1.1rem 1rem;
  }

  .qm-foot {
    padding: 0.75rem 1.1rem calc(0.9rem + env(safe-area-inset-bottom, 0px));
  }

  .qm-main {
    flex: 1;
  }
}

@media (max-width: 480px) {
  .flow-box {
    padding: 1rem;
  }

  .match-btn {
    font-size: 0.8rem;
  }
}

/* ==========================================================================
   Level, XP, registration, leaderboard and the cookie notice
   ========================================================================== */
.level-card,
.you-row {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.level-card {
  margin: 0.25rem 0 0.75rem;
  padding: 0.9rem 1rem;
  border: 1px solid var(--accent-border);
  border-radius: var(--radius-lg);
  background: var(--accent-soft);
}

.level-badge {
  display: grid;
  flex: none;
  place-items: center;
  width: 46px;
  height: 46px;
  border-radius: var(--radius);
  background: var(--accent-gradient);
  color: var(--on-accent);
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 700;
}

.level-info {
  display: grid;
  flex: 1;
  gap: 0.2rem;
  min-width: 0;
}

.level-info strong {
  font-size: 0.98rem;
}

.level-info span {
  font-size: 0.82rem;
  color: var(--soft);
}

.xp-track {
  height: 8px;
  margin-top: 0.3rem;
  overflow: hidden;
  border-radius: 4px;
  background: var(--accent-tint);
}

.xp-fill {
  height: 100%;
  border-radius: inherit;
  background: var(--accent-gradient);
  transition: width 0.6s var(--ease-out);
}

.register-box {
  margin-top: 1.1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
}

.register-box .modal-text {
  margin-bottom: 0.85rem;
}

.profile-foot {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem;
  margin-top: 0.5rem;
}

.profile-leaders-link {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--accent-text);
}

/* home page leaderboard */
.leaders-layout {
  display: grid;
  gap: 1.75rem;
  align-items: start;
}

@media (min-width: 900px) {
  .leaders-layout {
    grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr);
  }
}

.leaders-card {
  display: grid;
  gap: 0.9rem;
  padding: 1.25rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--surface);
}

.you-row {
  padding: 0.85rem 1rem;
  border-radius: var(--radius);
  background: var(--accent-soft);
}

.you-info {
  display: grid;
  flex: 1;
  min-width: 0;
}

.you-info span {
  font-size: 0.82rem;
  color: var(--soft);
}

.you-xp,
.leader-xp {
  font-family: var(--font-display);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

.leaders-list {
  display: grid;
  gap: 0.25rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.leaders-list:empty {
  display: none;
}

.leader-row {
  display: grid;
  grid-template-columns: 2rem minmax(0, 1fr) auto auto;
  align-items: center;
  gap: 0.75rem;
  min-height: 44px;
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius);
}

.leader-row:nth-child(-n + 3) .leader-rank {
  background: var(--accent-gradient);
  color: var(--on-accent);
}

.leader-row.is-you {
  outline: 2px solid var(--accent);
  background: var(--accent-soft);
}

.leader-rank {
  display: grid;
  place-items: center;
  width: 28px;
  height: 28px;
  border-radius: var(--radius-sm);
  background: var(--surface-subtle);
  font-size: 0.82rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

.leader-name {
  overflow: hidden;
  font-weight: 600;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.leader-level {
  font-size: 0.8rem;
  color: var(--faint);
}

.leaders-note {
  font-size: 0.88rem;
  color: var(--soft);
}

.leaders-note:empty {
  display: none;
}

.leaders-register {
  justify-self: start;
}

/* XP earned, on the quiz result */
.qm-xp {
  display: grid;
  gap: 0.2rem;
  margin-top: 1rem;
  font-family: var(--font-display);
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--accent-text);
}

.qm-xp span {
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--soft);
}

/* cookie notice */
.cookie-bar {
  position: fixed;
  right: 1rem;
  bottom: calc(1rem + env(safe-area-inset-bottom, 0px));
  left: 1rem;
  z-index: 90;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem 1rem;
  max-width: 560px;
  margin-inline: auto;
  padding: 0.9rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--surface);
  box-shadow: 0 18px 40px -20px rgba(11, 18, 32, 0.45);
}

.cookie-bar p {
  flex: 1 1 16rem;
  font-size: 0.88rem;
  color: var(--soft);
}

.anim .cookie-bar {
  animation: rise 0.45s var(--ease-out) 0.6s backwards;
}

.anim .cookie-bar.closing {
  animation: fade-down 0.22s var(--ease) forwards;
}

@keyframes fade-down {
  to {
    opacity: 0;
    transform: translateY(10px);
  }
}

/* ==========================================================================
   Toasts & confetti
   ========================================================================== */
.toast-container {
  position: fixed;
  left: 50%;
  bottom: 1.5rem;
  z-index: 120;
  display: grid;
  justify-items: center;
  gap: 0.5rem;
  width: max-content;
  max-width: calc(100% - 2rem);
  transform: translateX(-50%);
  pointer-events: none;
}

.toast-item {
  padding: 0.6rem 0.95rem;
  border-radius: var(--radius);
  background: var(--ink);
  color: var(--bg);
  font-size: 0.88rem;
  font-weight: 500;
  opacity: 0;
  transform: translateY(6px);
  transition: opacity 180ms var(--ease), transform 180ms var(--ease);
}

.toast-item.visible {
  opacity: 1;
  transform: none;
}

.confetti-container {
  position: fixed;
  inset: 0;
  z-index: 130;
  overflow: hidden;
  pointer-events: none;
}

.confetti-piece {
  position: absolute;
  top: -16px;
  width: 8px;
  height: 12px;
  animation: confettiFall 2.2s cubic-bezier(0.25, 0.46, 0.45, 0.94) forwards;
}

@keyframes confettiFall {
  to {
    top: 105%;
    rotate: 540deg;
    opacity: 0.6;
  }
}

/* ==========================================================================
   Motion
   Everything below runs only under html.anim, which the <head> script sets
   unless the visitor prefers reduced motion. Only opacity and transform are
   animated, so it stays smooth on phones.
   ========================================================================== */
@keyframes rise {
  from {
    opacity: 0;
    transform: translateY(18px);
  }
}

@keyframes reveal-up {
  from {
    opacity: 0.25;
    transform: translateY(32px) scale(0.98);
  }
}

@keyframes line-up {
  from {
    transform: translateY(105%);
  }
}

@keyframes ripple {
  0% {
    transform: scale(0);
    opacity: 0.35;
  }
  45% {
    opacity: 0.28;
  }
  100% {
    transform: scale(1);
    opacity: 0;
  }
}

@keyframes select-pop {
  0% { transform: scale(0.94); }
  60% { transform: scale(1.03); }
  100% { transform: scale(1); }
}

@keyframes star-pop {
  0% { transform: scale(0.3) rotate(-35deg); }
  60% { transform: scale(1.4) rotate(12deg); }
  100% { transform: none; }
}

@keyframes finger-swipe {
  0% { transform: translateY(16px); opacity: 0; }
  18% { opacity: 1; }
  62% { transform: translateY(-12px); opacity: 1; }
  85%, 100% { transform: translateY(-20px); opacity: 0; }
}

@keyframes trail-grow {
  0%, 15% { transform: scaleY(0); }
  62% { transform: scaleY(1); }
  100% { transform: scaleY(1); opacity: 0; }
}

@keyframes wheel-roll {
  0% { transform: translateY(0); opacity: 1; }
  70% { transform: translateY(9px); opacity: 0; }
  100% { transform: translateY(0); opacity: 0; }
}

/* the backdrop fades its colour, not its opacity, so the sheet inside stays solid */
@keyframes backdrop-in {
  from {
    background-color: transparent;
  }
}

@keyframes backdrop-out {
  to {
    background-color: transparent;
  }
}

@keyframes marker-sweep {
  from {
    transform: scaleX(0);
  }
}

@keyframes dialog-in {
  from {
    opacity: 0;
    transform: translateY(12px) scale(0.98);
  }
}

@keyframes dialog-out {
  to {
    opacity: 0;
    transform: translateY(8px) scale(0.98);
  }
}

@keyframes sheet-up {
  from {
    transform: translateY(100%);
  }
}

@keyframes sheet-down {
  to {
    transform: translateY(100%);
  }
}

@keyframes dot-pop {
  0% { transform: scale(0.3); }
  60% { transform: scale(1.25); }
  100% { transform: scale(1); }
}

@keyframes answer-pop {
  40% {
    transform: scale(1.025);
  }
}

@keyframes answer-shake {
  20% { transform: translateX(-6px); }
  40% { transform: translateX(5px); }
  60% { transform: translateX(-3px); }
  80% { transform: translateX(2px); }
}

@keyframes icon-turn {
  from {
    opacity: 0;
    transform: rotate(-90deg) scale(0.6);
  }
}

@keyframes glow-drift {
  from {
    transform: translate3d(0, 0, 0) scale(1);
  }
  to {
    transform: translate3d(-9%, 7%, 0) scale(1.18);
  }
}

.anim .hero::before,
.anim .page-head::before {
  animation: glow-drift 16s ease-in-out infinite alternate;
}

/* Gradient buttons: a light sheen sweeps across on hover (pointer devices) */
.btn:not(.btn-ghost):not(.btn-secondary)::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(105deg, transparent 30%, rgba(255, 255, 255, 0.32) 50%, transparent 70%);
  transform: translateX(-135%);
  pointer-events: none;
}

@media (hover: hover) and (pointer: fine) {
  .anim .btn:not(.btn-ghost):not(.btn-secondary):hover::after {
    transform: translateX(135%);
    transition: transform 850ms var(--ease-out);
  }
}

/* Hero and page headings: staggered entrance on load */
.anim .hero .reveal-line,
.anim .page-head .reveal-line {
  animation: rise 0.9s var(--ease-out) backwards;
}

/* title lines slide up out of a mask, one after another */
.anim .hero-title .reveal-line,
.anim .page-title .reveal-line {
  overflow: hidden;
  padding-bottom: 0.12em;
  margin-bottom: -0.12em;
  animation: none;
}

.anim .hero-title .reveal-line > span,
.anim .page-title .reveal-line > span {
  display: inline-block;
  animation: line-up 1.05s var(--ease-out) backwards;
}

.anim .hero-title .reveal-line:nth-child(1) > span,
.anim .page-title .reveal-line > span { animation-delay: 120ms; }
.anim .hero-title .reveal-line:nth-child(2) > span { animation-delay: 240ms; }
.anim .hero-sub,
.anim .page-sub { animation-delay: 420ms; }
.anim .hero-actions { animation-delay: 540ms; }

.anim .scroll-hint {
  animation: rise 0.9s var(--ease-out) 1.2s backwards;
}

.anim .scroll-hint-finger svg {
  animation: finger-swipe 1.9s var(--ease) 2s infinite;
}

.anim .scroll-hint-finger::before {
  transform-origin: bottom center;
  animation: trail-grow 1.9s var(--ease) 2s infinite;
}

.anim .scroll-hint-mouse .wheel {
  animation: wheel-roll 1.6s var(--ease) 2s infinite;
}

/* The entrance stays on its first frame until main.js has the fonts (adds .anim-go);
   !important because every `animation:` shorthand above resets the play state */
.anim:not(.anim-go) .hero *,
.anim:not(.anim-go) .hero *::before,
.anim:not(.anim-go) .page-head *,
.anim:not(.anim-go) .page-head *::before {
  animation-play-state: paused !important;
}

/* The cookie bar on a first visit covers the finger: it waits hidden, then starts from the top */
.anim.has-cookie-bar .scroll-hint,
.anim.has-cookie-bar .scroll-hint-finger svg,
.anim.has-cookie-bar .scroll-hint-finger::before,
.anim.has-cookie-bar .scroll-hint-mouse .wheel {
  animation: none;
}

.has-cookie-bar .scroll-hint {
  visibility: hidden;
}

.anim.cookie-closed .scroll-hint { animation-delay: 0.1s; }

.anim.cookie-closed .scroll-hint-finger svg,
.anim.cookie-closed .scroll-hint-finger::before,
.anim.cookie-closed .scroll-hint-mouse .wheel {
  animation-delay: 0.7s;
}

/* «за минуту»: the blue box sweeps in like a highlighter */
.anim .hero-invert {
  background: transparent;
}

.anim .hero-invert::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  border-radius: inherit;
  background: var(--accent-gradient);
  transform-origin: left center;
  animation: marker-sweep 0.8s var(--ease-out) 0.75s backwards;
}

/* Scroll reveal: main.js adds .visible when a block enters the screen */
.anim .reveal.visible {
  animation: reveal-up 1s var(--ease-out) var(--stagger, 0ms) backwards;
}

.anim .grid > .reveal:nth-child(2) { --stagger: 90ms; }
.anim .grid > .reveal:nth-child(3) { --stagger: 180ms; }
.anim .grid > .reveal:nth-child(4) { --stagger: 270ms; }
.anim .grid > .reveal:nth-child(5) { --stagger: 360ms; }

.anim .lesson-flow > .reveal:nth-child(3) { --stagger: 60ms; }
.anim .lesson-flow > .reveal:nth-child(4) { --stagger: 120ms; }
.anim .lesson-flow > .reveal:nth-child(5) { --stagger: 180ms; }
.anim .lesson-flow > .reveal:nth-child(6) { --stagger: 240ms; }
.anim .lesson-flow > .reveal:nth-child(7) { --stagger: 300ms; }

/* Lesson cards and topic chips cascade in whenever the list is rebuilt */
.anim .lessons-grid > .lesson-card {
  animation: reveal-up 0.8s var(--ease-out) backwards;
}

.anim .lessons-grid > .lesson-card:nth-child(2) { animation-delay: 60ms; }
.anim .lessons-grid > .lesson-card:nth-child(3) { animation-delay: 120ms; }
.anim .lessons-grid > .lesson-card:nth-child(4) { animation-delay: 180ms; }
.anim .lessons-grid > .lesson-card:nth-child(5) { animation-delay: 240ms; }
.anim .lessons-grid > .lesson-card:nth-child(6) { animation-delay: 300ms; }
.anim .lessons-grid > .lesson-card:nth-child(n + 7) { animation-delay: 360ms; }

.anim .topic-choices > .topic-chip {
  animation: rise 0.45s var(--ease-out) backwards;
}

.anim .topic-choices > .topic-chip:nth-child(2) { animation-delay: 35ms; }
.anim .topic-choices > .topic-chip:nth-child(3) { animation-delay: 70ms; }
.anim .topic-choices > .topic-chip:nth-child(4) { animation-delay: 105ms; }
.anim .topic-choices > .topic-chip:nth-child(5) { animation-delay: 140ms; }
.anim .topic-choices > .topic-chip:nth-child(n + 6) { animation-delay: 175ms; }

/* Quiz: the box slides open, answers react to the check */

/* tapping a choice makes it pop */
.anim .choice-card.selected,
.anim .topic-chip.selected,
.anim .filter-tab-btn.active,
.anim .quiz-option-label.checked {
  animation: select-pop 0.45s var(--spring);
}

.anim .bookmark-action-btn.active .bookmark-icon {
  display: inline-block;
  animation: star-pop 0.6s var(--spring);
}

.anim .quiz-option-label.is-correct {
  animation: answer-pop 0.4s var(--ease-out);
}

.anim .quiz-option-label.is-wrong {
  animation: answer-shake 0.45s var(--ease);
}

/* tasks: marks pop in, the readout bumps, the frame reacts to the check */
.anim .task-fig .pop {
  transform-box: fill-box;
  transform-origin: center;
  animation: dot-pop 0.45s var(--spring);
}

.anim .task-step-out.bump {
  animation: select-pop 0.35s var(--spring);
}

.anim .is-correct > .task {
  animation: answer-pop 0.4s var(--ease-out);
}

.anim .is-wrong > .task {
  animation: answer-shake 0.45s var(--ease);
}

.anim .task-answer {
  animation: rise 0.45s var(--ease-out) backwards;
}

/* Profile dialog / bottom sheet */
.anim .modal-backdrop {
  animation: backdrop-in 0.25s var(--ease) backwards;
}

.anim .modal {
  animation: dialog-in 0.34s var(--ease-out) backwards;
}

.anim .modal-backdrop.closing {
  animation: backdrop-out 0.22s var(--ease) forwards;
}

.anim .modal-backdrop.closing .modal {
  animation: dialog-out 0.22s var(--ease) forwards;
}

/* Toasts rise from below */
.toast-item {
  transform: translateY(16px) scale(0.94);
  transition: opacity 300ms var(--ease-out), transform 480ms var(--spring);
}

/* Theme switch: colours cross-fade, the icon turns */
.theme-switching,
.theme-switching *,
.theme-switching *::before,
.theme-switching *::after {
  transition: background-color 0.35s var(--ease), color 0.35s var(--ease), border-color 0.35s var(--ease),
    box-shadow 0.35s var(--ease) !important;
}

.theme-switching .theme-icon svg {
  animation: icon-turn 0.45s var(--ease-out);
}

/* Phones: the profile is a bottom sheet, menu items cascade in */
@media (max-width: 860px) {
  .anim .modal {
    animation: sheet-up 0.42s var(--ease-out) backwards;
  }

  .anim .modal-backdrop.closing .modal {
    animation: sheet-down 0.22s var(--ease) forwards;
  }

  .anim .nav-links.open > * {
    animation: rise 0.45s var(--ease-out) backwards;
  }

  .anim .nav-links.open > :nth-child(2) { animation-delay: 30ms; }
  .anim .nav-links.open > :nth-child(3) { animation-delay: 60ms; }
  .anim .nav-links.open > :nth-child(4) { animation-delay: 90ms; }
  .anim .nav-links.open > :nth-child(5) { animation-delay: 120ms; }
  .anim .nav-links.open > :nth-child(6) { animation-delay: 150ms; }
  .anim .nav-links.open > :nth-child(7) { animation-delay: 180ms; }
  .anim .nav-links.open > :nth-child(n + 8) { animation-delay: 210ms; }
}

/* Click feedback: a ripple spreads from the touch point (main.js),
   the control presses in fast and springs back */
.btn,
.card,
.choice-card,
.topic-chip,
.filter-tab-btn,
.quiz-option-label,
.nav-quick-subject,
.theme-toggle-btn,
.nav-profile-btn,
.reset-button,
.quiz-unlock-btn,
.card-icon-action,
.order-card,
.match-btn,
.term-btn,
.sign-btn,
.scroll-hint {
  position: relative;
  overflow: hidden;
  transition-property: transform, background-color, border-color, color, box-shadow, opacity;
  transition-duration: 480ms, 200ms, 200ms, 200ms, 300ms, 300ms;
  transition-timing-function: var(--spring), var(--ease), var(--ease), var(--ease), var(--ease-out), var(--ease);
}

.scroll-hint {
  position: absolute;
  overflow: visible;
}

.ripple {
  position: absolute;
  border-radius: 50%;
  background: currentColor;
  opacity: 0;
  transform: scale(0);
  pointer-events: none;
  animation: ripple 0.7s cubic-bezier(0.22, 0.61, 0.36, 1) forwards;
}

/* Circular theme switch (View Transitions); main.js animates the circle */
.theme-vt::view-transition-old(root),
.theme-vt::view-transition-new(root) {
  animation: none;
  mix-blend-mode: normal;
}

/* Page to page: a short fade instead of a hard cut (browsers that support it) */
@media (prefers-reduced-motion: no-preference) {
  @view-transition {
    navigation: auto;
  }
}

::view-transition-old(root) {
  animation: 180ms cubic-bezier(0.4, 0, 1, 1) both vt-out;
}

::view-transition-new(root) {
  animation: 320ms cubic-bezier(0, 0, 0.2, 1) 60ms both vt-in;
}

.theme-vt::view-transition-old(root),
.theme-vt::view-transition-new(root) {
  animation: none;
}

@keyframes vt-out {
  to {
    opacity: 0;
  }
}

@keyframes vt-in {
  from {
    opacity: 0;
  }
}

/* ==========================================================================
   Hover effects only where a real pointer exists (no sticky hover on phones)
   ========================================================================== */
@media (hover: hover) and (pointer: fine) {
  .btn:hover {
    filter: brightness(1.08) saturate(1.05);
    transform: translateY(-2px);
    box-shadow: 0 12px 26px -12px var(--accent-glow);
  }
  .btn-ghost:hover,
  .btn-secondary:hover {
    filter: none;
    background: var(--surface-subtle);
    border-color: var(--accent-border);
    color: var(--ink);
    box-shadow: none;
  }
  .nav-link:hover { color: var(--ink); }
  .theme-toggle-btn:hover,
  .nav-profile-btn:hover,
  .burger:hover,
  .reset-button:hover,
  .quiz-unlock-btn:hover,
  .flow-back:hover,
  .progress-step:not(:disabled):not(.active):hover,
  .modal-close:hover { background: var(--surface-subtle); }
  .card:hover,
  .choice-card:hover,
  .topic-chip:hover,
  .filter-tab-btn:hover,
  .quiz-option-label:hover { border-color: var(--accent-border); }
  .choice-card:hover,
  .topic-chip:hover,
  .filter-tab-btn:hover { transform: translateY(-2px); }
  .filter-tab-btn:hover { color: var(--ink); }
  .card:hover { transform: translateY(-4px); box-shadow: 0 18px 36px -22px var(--accent-glow); }
  .lesson-card:hover { border-color: var(--accent-border); box-shadow: 0 18px 36px -24px var(--accent-glow); }
  .scroll-hint:hover { transform: translate(-50%, -3px); }
  .subject-card:hover .card-arrow { color: var(--ink); transform: translateX(4px); }
  .lesson-media:hover .play-badge::before { background: rgba(0, 0, 0, 0.8); transform: scale(1.08); }
  .lesson-media:not(.is-pending):hover img { transform: scale(1.035); }
  .quiz-unlock-btn:hover { background: var(--accent-tint); border-color: var(--accent); }
  .order-card:not(.is-gone):hover,
  .match-btn:hover,
  .term-btn:hover { border-color: var(--accent); }
}

/* press states come after hover so a click always shows the press */
.btn:active,
.card:active,
.choice-card:active,
.topic-chip:active,
.filter-tab-btn:active,
.quiz-option-label:active,
.nav-quick-subject:active,
.theme-toggle-btn:active,
.nav-profile-btn:active,
.reset-button:active,
.quiz-unlock-btn:active,
.card-icon-action:active,
.flow-back:active,
.order-card:active,
.match-btn:active,
.term-btn:active,
.sign-btn:active {
  transform: scale(0.95);
  transition-duration: 90ms;
}

.card:active {
  transform: scale(0.98);
}

/* finger on touch screens, mouse wheel where a real pointer exists */
@media (hover: hover) and (pointer: fine) {
  .scroll-hint-finger { display: none; }
  .scroll-hint-mouse { display: grid; }
}

/* desktop navigation: a blue underline slides in */
@media (min-width: 861px) {
  .nav-link {
    position: relative;
  }

  .nav-link::after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    bottom: -6px;
    height: 2px;
    border-radius: 2px;
    background: var(--accent);
    transform: scaleX(0);
    transition: transform 0.4s var(--ease-out);
  }

  .nav-link.active::after {
    transform: scaleX(1);
  }
}

@media (min-width: 861px) and (hover: hover) {
  .nav-link:hover::after {
    transform: scaleX(1);
  }
}

@media (hover: none) {
  .search-kbd-hint { display: none; }
}

/* ==========================================================================
   Phones & small tablets
   ========================================================================== */
@media (max-width: 860px) {
  :root {
    --header-h: 56px;
  }

  .container {
    width: calc(100% - 2rem);
  }

  .nav-inner > .register-open {
    display: none;
  }

  .nav-actions {
    margin-left: auto;
  }

  .nav-profile-btn,
  .burger {
    display: inline-flex;
  }

  /* Drop-down menu panel under the header */
  .nav-links {
    position: fixed;
    top: calc(var(--header-h) + env(safe-area-inset-top, 0px));
    left: 0;
    right: 0;
    z-index: 2;
    display: grid;
    gap: 0;
    max-height: calc(100vh - var(--header-h));
    max-height: calc(100dvh - var(--header-h) - env(safe-area-inset-top, 0px));
    overflow-y: auto;
    overscroll-behavior: contain;
    margin: 0;
    padding: 0.5rem 1rem calc(1.25rem + env(safe-area-inset-bottom, 0px));
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    visibility: hidden;
    opacity: 0;
    transform: translateY(-10px);
    transition: opacity 200ms var(--ease), transform 200ms var(--ease), visibility 0s linear 200ms;
  }

  .nav-links.open {
    visibility: visible;
    opacity: 1;
    transform: none;
    transition: opacity 280ms var(--ease-out), transform 280ms var(--ease-out);
  }

  .nav-mobile-header {
    display: block;
    padding: 0.5rem 0 0.75rem;
    font-size: 0.85rem;
    color: var(--faint);
  }

  .greeting-avatar {
    display: none;
  }

  .nav-quick-subjects {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.5rem;
    padding-bottom: 0.75rem;
  }

  .nav-quick-subject {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    min-height: 48px;
    padding: 0.6rem 0.8rem;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-size: 0.9rem;
    font-weight: 600;
  }

  .nav-quick-subject span:first-child {
    width: 1.2em;
    text-align: center;
    font-weight: 700;
  }

  .nav-quick-subject.math span:first-child { color: var(--math); }
  .nav-quick-subject.russian span:first-child { color: var(--rus); }

  .nav-link {
    justify-content: space-between;
    min-height: 50px;
    border-top: 1px solid var(--border);
    font-size: 1rem;
    color: var(--ink);
  }

  .nav-link.active {
    color: var(--accent-text);
  }

  .nav-link-arrow {
    display: inline;
    color: var(--faint);
  }

  .nav-mobile-footer {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.5rem;
    padding-top: 0.9rem;
    border-top: 1px solid var(--border);
  }

  .nav-mobile-footer .btn,
  .nav-mobile-footer .theme-toggle-btn {
    width: 100%;
    min-height: 46px;
    margin: 0 !important;
  }

  .nav-backdrop {
    position: fixed;
    top: calc(var(--header-h) + env(safe-area-inset-top, 0px));
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 1;
    display: block;
    background: var(--overlay);
    opacity: 0;
    pointer-events: none;
    transition: opacity var(--fast) var(--ease);
  }

  .nav-backdrop.open {
    opacity: 1;
    pointer-events: auto;
  }

  .toast-container {
    bottom: calc(1rem + env(safe-area-inset-bottom, 0px));
  }

  /* Profile becomes a bottom sheet */
  .modal-backdrop {
    align-items: end;
    padding: 0;
  }

  .modal {
    width: 100%;
    max-height: 90vh;
    max-height: 90dvh;
    padding: 1.5rem 1.25rem calc(1.5rem + env(safe-area-inset-bottom, 0px));
    border-width: 1px 0 0;
    border-radius: 16px 16px 0 0;
  }

  .sheet-handle {
    display: block;
    width: 36px;
    height: 4px;
    margin: -0.5rem auto 1rem;
    border-radius: 2px;
    background: var(--border-strong);
  }

  .grade-guide-item {
    grid-template-columns: 1fr;
  }

  .grade-choices {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (max-width: 480px) {
  .hero-actions .btn {
    flex: 1 1 100%;
  }

  .flow-step {
    padding: 1rem;
  }

  .subject-card {
    padding: 1rem;
  }

  .subject-detail-card {
    padding: 1.25rem;
  }

  .step-text {
    font-size: 0.8rem;
  }

  .lesson-body {
    padding: 1rem;
  }

  .quiz-lock-status {
    flex-wrap: wrap;
  }

  .quiz-unlock-btn {
    width: 100%;
  }
}

/* ==========================================================================
   Accessibility & print
   ========================================================================== */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}

@media print {
  .nav,
  .footer,
  .modal-backdrop,
  .toast-container,
  .filter-tabs-bar,
  .lesson-search-container,
  .reset-button,
  .lesson-card-top-actions {
    display: none !important;
  }

  body {
    padding: 0;
    background: #fff;
    color: #000;
  }

  .lesson-card,
  .card {
    break-inside: avoid;
  }
}

/* ==========================================================================
   Tasks: shade a fraction, place a point, fill letter gaps, build from tiles
   ========================================================================== */
.task-fig.fig-slices-pie { max-width: 230px; }
.task-fig.fig-slices-bar { max-width: 420px; }
.f-slice { fill: var(--surface); stroke: var(--ink); stroke-width: 2.5; stroke-linejoin: round; cursor: pointer; transition: fill var(--fast) var(--ease); }
.f-slice.is-on { fill: var(--fig-teal); }
.f-slice.is-given { fill: var(--fig-mustard); cursor: default; }
.f-slice:focus-visible { outline: none; stroke: var(--accent); stroke-width: 4; }
@media (hover: hover) and (pointer: fine) {
  .f-slice:not(.is-given):not(.is-on):hover { fill: var(--fig-teal-soft); }
}

.f-place-stem { stroke: var(--accent); stroke-width: 2.5; stroke-linecap: round; }
.f-place-dot { fill: var(--accent); stroke: var(--surface); stroke-width: 3; }
.f-place-hit { fill: transparent; cursor: grab; }
.f-place.is-answer .f-place-dot { fill: var(--success); }
.f-place.is-answer .f-place-stem { stroke: var(--success); }

.gap-row {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.55rem 1.1rem;
  padding: 0.3rem 0;
  font-family: var(--font-display);
  font-size: 1.35rem;
  font-weight: 700;
}
.gap-word { display: inline-flex; align-items: center; gap: 2px; white-space: nowrap; }
.gap-hole {
  display: inline-grid;
  place-items: center;
  min-width: 34px;
  height: 46px;
  padding: 0 4px;
  border: 1.5px dashed var(--border-strong);
  border-radius: 8px;
  background: transparent;
  color: var(--accent-text);
  font: inherit;
  transition: background var(--fast) var(--ease), border-color var(--fast) var(--ease);
}
.gap-hole.is-on { border-style: solid; border-color: var(--accent); background: var(--accent-soft); }
.gap-hole.is-answer { border-style: solid; border-color: var(--success); background: var(--success-soft); color: var(--success); }
.gap-hole.is-miss { border-style: solid; border-color: var(--danger); background: var(--danger-soft); color: var(--danger); }

.build-board { display: grid; gap: 0.8rem; }
.build-line,
.build-pool {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: 0.4rem;
}
.build-line {
  min-height: 62px;
  padding: 0.35rem;
  border: 2px dashed var(--border-strong);
  border-radius: var(--radius);
}
.build-empty { font-size: 0.82rem; color: var(--faint); }
.build-tile {
  display: grid;
  place-items: center;
  min-width: 46px;
  height: 48px;
  padding: 0 0.6rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  font-family: var(--font-display);
  font-size: 1.12rem;
  font-weight: 700;
  white-space: nowrap;
}
.build-tile.is-placed { border-color: transparent; background: var(--fig-teal); color: #ffffff; }
.build-tile.is-gone { display: none; }

/* ==========================================================================
   Quiz dialog: question entrance, feedback, readiness, result ring
   ========================================================================== */
.qm-feedback { display: flex; align-items: flex-start; gap: 0.65rem; }
.qm-fb-icon {
  display: inline-grid;
  place-items: center;
  flex: none;
  width: 26px;
  height: 26px;
  margin-top: 1px;
  border-radius: 50%;
  background: currentColor;
  font-size: 0.85rem;
  font-weight: 800;
  line-height: 1;
}
/* the icon glyph sits on the coloured circle in the page background colour */
.qm-fb-icon { color: inherit; }
.qm-feedback.success .qm-fb-icon { background: var(--success); color: var(--surface); }
.qm-feedback.error .qm-fb-icon { background: var(--danger); color: var(--surface); }
.qm-feedback.info .qm-fb-icon { background: var(--accent); color: var(--on-accent); font-style: italic; font-family: Georgia, serif; }
.qm-fb-text { min-width: 0; }

.qm-main { transition: opacity var(--fast) var(--ease), transform var(--fast) var(--ease); }
.qm-main.is-waiting { opacity: 0.55; }

.qm-ring { position: relative; width: 150px; height: 150px; margin: 0 auto; }
.qm-ring svg { width: 100%; height: 100%; transform: rotate(-90deg); }
.qm-ring-bg, .qm-ring-fg { fill: none; stroke-width: 10; }
.qm-ring-bg { stroke: var(--border); }
.qm-ring-fg {
  stroke: var(--accent);
  stroke-linecap: round;
  stroke-dasharray: 100;
  stroke-dashoffset: calc(100 - var(--k) * 100);
}
.qm-result.is-all .qm-ring-fg { stroke: var(--success); }
.qm-ring .qm-score { position: absolute; inset: 0; display: grid; place-content: center; line-height: 1.1; }
.qm-ring .qm-score span { font-size: 3rem; }
.qm-dots { display: flex; justify-content: center; gap: 0.45rem; margin-top: 0.9rem; }
.qm-dots i { width: 12px; height: 12px; border-radius: 50%; }
.qm-dots i.is-right { background: var(--success); }
.qm-dots i.is-wrong { background: var(--danger); }

/* answer buttons in tasks feel pressable */
.choice-opt, .match-btn, .tok, .build-tile, .order-card, .gap-hole, .punct-gap, .sort-chip {
  transition-property: transform, background-color, border-color, color, box-shadow;
  transition-duration: 160ms;
}
.choice-opt:active:not(:disabled), .match-btn:active:not(:disabled), .tok:active:not(:disabled),
.build-tile:active:not(:disabled), .order-card:active:not(:disabled), .gap-hole:active:not(:disabled),
.punct-gap:active:not(:disabled) {
  transform: scale(0.96);
}
@media (hover: hover) and (pointer: fine) {
  .choice-opt:hover:not(:disabled), .match-btn:hover:not(:disabled), .build-tile:hover:not(:disabled):not(.is-placed),
  .sort-chip:hover:not(:disabled):not(.is-dragging) {
    transform: translateY(-2px);
  }
}

@keyframes q-in { from { opacity: 0; transform: translateX(28px); } }
@keyframes fb-in { from { opacity: 0; transform: translateY(10px) scale(0.98); } }
@keyframes ring-fill { from { stroke-dashoffset: 100; } }
@keyframes dot-in { from { opacity: 0; transform: scale(0.2); } }

.anim .qm-body .quiz-question-item { animation: q-in 0.38s var(--ease-out) backwards; }
.anim .qm-feedback.is-in { animation: fb-in 0.32s var(--ease-out) backwards; }
.anim .qm-feedback.is-in .qm-fb-icon { animation: dot-pop 0.45s var(--spring) 0.1s backwards; }
.anim .qm-ring-fg { animation: ring-fill 0.9s var(--ease-out) 0.1s backwards; }
.anim .qm-result { animation: rise 0.45s var(--ease-out) backwards; }
.anim .qm-dots i { animation: dot-in 0.35s var(--spring) backwards; animation-delay: calc(0.5s + var(--d) * 0.08s); }
.anim .sort-board.is-sorted .sort-zone { animation: answer-pop 0.4s var(--ease-out); }

/* ===================================================================
   Pause on the puzzle: a guess between the video's question and its solution
   =================================================================== */
.vstop {
  margin: 0;
  padding: 1rem 1rem 1.1rem;
  border-bottom: 1px solid var(--border);
  background: var(--accent-soft);
  display: grid;
  gap: 0.7rem;
  animation: vstop-in 320ms var(--ease-out) both;
}
.vstop.is-out { animation: vstop-out 200ms ease-in both; }
@keyframes vstop-in { from { opacity: 0; transform: translateY(-8px); } }
@keyframes vstop-out { to { opacity: 0; transform: translateY(-6px); } }
.vstop-label {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin: 0;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--accent-text);
}
.vstop-icon { width: 0.7rem; height: 0.8rem; border-left: 0.22rem solid currentColor; border-right: 0.22rem solid currentColor; }
.vstop-q { margin: 0; font-family: var(--font-display); font-size: 1.05rem; font-weight: 700; line-height: 1.3; color: var(--ink); }
.vstop-opts { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.vstop-opt {
  flex: 1 1 8rem;
  min-height: 46px;
  padding: 0.55rem 0.9rem;
  border: 1.5px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  font: inherit;
  font-weight: 700;
  cursor: pointer;
  transition: border-color var(--fast) var(--ease), background var(--fast) var(--ease), transform var(--fast) var(--ease);
}
.vstop-opt:hover:not(:disabled) { border-color: var(--accent); }
.vstop-opt:active:not(:disabled) { transform: scale(0.97); }
.vstop-opt:disabled { cursor: default; opacity: 0.6; }
.vstop-opt.is-right { opacity: 1; border-color: var(--success); background: var(--success-soft); color: var(--success); }
.vstop-opt.is-wrong { opacity: 1; border-color: var(--danger); background: var(--danger-soft); color: var(--danger); }
.vstop-msg { margin: 0; font-weight: 600; }
.vstop-msg.is-right { color: var(--success); }
.vstop-msg.is-wrong { color: var(--danger); }
.vstop-go { justify-self: start; }
@media (prefers-reduced-motion: reduce) { .vstop, .vstop.is-out { animation: none; } }

/* ===================================================================
   Quiz question: story, then the instruction in bold; a how-to chip; the lesson rule on demand
   =================================================================== */
.quiz-q-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  margin: 0 0 0.45rem;
  padding: 0.18rem 0.6rem;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent-text);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}
.quiz-q-tag::before {
  content: "";
  width: 0; height: 0;
  border-left: 0.5rem solid currentColor;
  border-top: 0.3rem solid transparent;
  border-bottom: 0.3rem solid transparent;
}
.quiz-q-context {
  margin: 0 0 0.4rem;
  color: var(--soft);
  font-size: 0.93rem;
  line-height: 1.5;
}
.qm-body .quiz-q-title {
  margin-bottom: 0.55rem;
  color: var(--ink);
  font-size: 1.02rem;
  font-weight: 700;
  line-height: 1.4;
}
.quiz-rule-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  margin: 0 0 0.6rem;
  padding: 0.15rem 0;
  border: 0;
  background: none;
  color: var(--accent-text);
  font: inherit;
  font-size: 0.84rem;
  font-weight: 600;
  cursor: pointer;
}
.quiz-rule-btn::before {
  content: "?";
  display: inline-grid;
  place-items: center;
  width: 1.15rem;
  height: 1.15rem;
  border: 1.5px solid currentColor;
  border-radius: 50%;
  font-size: 0.72rem;
  font-weight: 800;
}
.quiz-rule-btn:hover { text-decoration: underline; }
.quiz-rule {
  margin: 0 0 0.75rem;
  padding: 0.6rem 0.8rem;
  border-left: 3px solid var(--accent);
  border-radius: 0 var(--radius) var(--radius) 0;
  background: var(--accent-soft);
  animation: fb-in 220ms var(--ease-out) both;
}
.quiz-rule-text { margin: 0; color: var(--ink); font-size: 0.86rem; line-height: 1.5; }
/* the how-to line goes first, as a chip, so the student knows what to do before looking at the drawing */
.qm-body .task-hint {
  order: -1;
  justify-self: start;
  margin: 0;
  padding: 0.3rem 0.75rem;
  border-radius: 999px;
  background: var(--surface);
  border: 1px solid var(--accent-border);
  color: var(--accent-text);
  font-size: 0.8rem;
  font-weight: 600;
  text-align: left;
  line-height: 1.35;
}
.qm-body .quiz-question-item > .task-hint { display: inline-block; margin-bottom: 0.6rem; }
@media (prefers-reduced-motion: reduce) { .quiz-rule { animation: none; } }
.f-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.3rem 1rem; font-size: 0.85rem; font-weight: 600; color: var(--ink); }
.f-legend span { display: inline-flex; align-items: center; gap: 0.35rem; }
.f-legend line { stroke-width: 3; }

/* ===================================================================
   Scenes: illustrated tasks in the videos' flat style (js/scenes*.js)
   =================================================================== */
:root {
  --sc-paper: #f3ece2; --sc-ink: #1c1a2e; --sc-cream: #fbf6ee; --sc-line: #d8cdbf;
  --sc-teal: #1c8b76; --sc-gold: #efb038; --sc-red: #e1513a; --sc-blue: #3d7be0; --sc-violet: #8a6fd1;
  --sc-crust: #d99a3e; --sc-cheese: #f4c860; --sc-soft: #7a7385;
}
:root[data-theme="dark"] {
  --sc-paper: #1d1c26; --sc-ink: #efe5d9; --sc-cream: #2a2836; --sc-line: #3a3848;
  --sc-teal: #34b89c; --sc-gold: #f2be52; --sc-red: #f2705a; --sc-blue: #6ea0ff; --sc-violet: #a68ce8;
  --sc-crust: #c98b38; --sc-cheese: #e9bd57; --sc-soft: #a59eb5;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --sc-paper: #1d1c26; --sc-ink: #efe5d9; --sc-cream: #2a2836; --sc-line: #3a3848;
    --sc-teal: #34b89c; --sc-gold: #f2be52; --sc-red: #f2705a; --sc-blue: #6ea0ff; --sc-violet: #a68ce8;
    --sc-crust: #c98b38; --sc-cheese: #e9bd57; --sc-soft: #a59eb5;
  }
}
.task-scene { padding: 0.6rem; }
.scene-fig { width: 100%; height: auto; display: block; touch-action: manipulation; user-select: none; -webkit-user-select: none; }
.scene-fig text { font-family: "Rubik", var(--font-display); font-weight: 700; fill: var(--sc-ink); }
.sc-paper { fill: var(--sc-paper); }
.sc-teal, .sc-teal > * { fill: var(--sc-teal); }
.sc-gold, .sc-gold > * { fill: var(--sc-gold); }
.sc-red, .sc-red > * { fill: var(--sc-red); }
.sc-blue, .sc-blue > * { fill: var(--sc-blue); }
.sc-violet, .sc-violet > * { fill: var(--sc-violet); }
.sc-ink, .sc-ink > * { fill: var(--sc-ink); }
.sc-cream, .sc-cream > * { fill: var(--sc-cream); }
.sc-soft { fill: var(--sc-soft); }
.sc-crust { fill: var(--sc-crust); }
.sc-cheese { fill: var(--sc-cheese); }
.sc-stroke { fill: none; stroke: var(--sc-ink); stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
.sc-zone { fill: var(--sc-cream); stroke: var(--sc-line); stroke-width: 2.5; stroke-dasharray: 8 6; transition: stroke var(--fast) var(--ease), fill var(--fast) var(--ease); cursor: pointer; }
.sc-zone.is-over, .scene-fig.is-picking .sc-zone:hover { stroke: var(--sc-teal); fill: color-mix(in srgb, var(--sc-teal) 10%, var(--sc-cream)); }
.scene-fig.is-picking .sc-zone { stroke: var(--sc-teal); }
.sc-zone:focus-visible, .sc-item:focus-visible, .sc-tap:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.sc-zone-label { font-size: 15px; fill: var(--sc-soft) !important; }
.sc-item { cursor: grab; touch-action: none; }
.sc-item.is-dragging { cursor: grabbing; filter: drop-shadow(0 6px 6px rgba(0, 0, 0, 0.25)); }
.sc-item.is-picked { filter: drop-shadow(0 0 0 var(--accent)) drop-shadow(0 0 4px var(--accent)); }
.scene-fig.is-locked .sc-item, .scene-fig.is-locked .sc-zone, .task.is-locked .sc-tap { cursor: default; pointer-events: none; }
.sc-tap { cursor: pointer; }
.sc-tap:hover { filter: brightness(1.06); }
.sc-card-bg { fill: var(--sc-cream); stroke: var(--sc-ink); stroke-width: 2.5; }
.sc-card-text { font-size: 18px; }
.sc-coin-text { font-size: 15px; fill: var(--sc-ink) !important; }
.sc-c-teal { fill: var(--sc-teal); } .sc-c-gold { fill: var(--sc-gold); } .sc-c-red { fill: var(--sc-red); }
.sc-burst circle { animation: sc-burst 850ms cubic-bezier(.2,.8,.2,1) forwards; }
@keyframes sc-burst { to { transform: translate(var(--dx), var(--dy)) scale(0.3); opacity: 0; } }
.sc-good { stroke: var(--success) !important; }
.sc-bad { stroke: var(--danger) !important; }
.sc-btn-row { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.5rem; }
@media (prefers-reduced-motion: reduce) { .sc-burst { display: none; } }
.sc-cut { stroke: var(--sc-crust); stroke-width: 4; stroke-linecap: round; stroke-dasharray: 120; }
.sc-name { font-size: 16px; }
.sc-share { font-size: 20px; fill: var(--sc-ink); }
.sc-dot { display: inline-block; width: 0.7em; height: 0.7em; margin-right: 0.35em; border-radius: 50%; vertical-align: -0.05em; }
span.sc-teal { background: var(--sc-teal); } span.sc-gold { background: var(--sc-gold); } span.sc-red { background: var(--sc-red); }
span.sc-blue { background: var(--sc-blue); } span.sc-violet { background: var(--sc-violet); }
/* second try */
.quiz-question-item.is-shake { animation: q-shake 420ms ease; }
@keyframes q-shake { 0%, 100% { transform: none; } 20% { transform: translateX(-7px); } 40% { transform: translateX(6px); } 60% { transform: translateX(-4px); } 80% { transform: translateX(2px); } }
.qm-giveup { display: inline; margin-left: 0.35rem; padding: 0; border: 0; background: none; color: inherit; font: inherit; font-weight: 700; text-decoration: underline; cursor: pointer; }
.qm-dots i.is-second { background: var(--sc-gold, #efb038); }
@media (prefers-reduced-motion: reduce) { .quiz-question-item.is-shake { animation: none; } }

/* scenes: grade 6 */
/* math6 scenes */
.scene-fig .sc-tx { font-size: 14px; }
.scene-fig .sc-tx-m { font-size: 16px; }
.scene-fig .sc-tx-b { font-size: 22px; }
.scene-fig .sc-tx-soft { fill: var(--sc-soft); }
.scene-fig .sc-tx-teal { fill: var(--sc-teal); }
.scene-fig .sc-tx-red { fill: var(--sc-red); }
.scene-fig .sc-tx-gold { fill: var(--sc-gold); }
.scene-fig .sc-tx-cream { fill: var(--sc-cream); }
.sc-thin { fill: none; stroke: var(--sc-ink); stroke-width: 2; stroke-linecap: round; }
.sc-hair { fill: none; stroke: var(--sc-line); stroke-width: 1.5; }
.sc-glass { fill: var(--sc-blue); fill-opacity: 0.14; }
.sc-sugar { fill: #ffffff; }
.sc-hit { fill: transparent; }
.sc-ghost { fill: var(--sc-soft); fill-opacity: 0.35; }
.sc-picked-bar { fill: var(--sc-gold); }
.scene-pizza-roll .sc-pizza-g, .scene-thermometer .sc-handle, .scene-juice-pour .sc-drag, .scene-sugar-cup .sc-drag { cursor: grab; touch-action: none; }
.scene-fig .sc-tx-l { font-size: 19px; }

/* scenes: grade 7 */
/* math7 scenes (js/scenes-math7.js) */
.sc-m7-s { font-size: 14px; }
.sc-m7-t { font-size: 16px; }
.sc-m7-b { font-size: 22px; }
.sc-m7-xl { font-size: 32px; }
.sc-m7-on { fill: var(--sc-cream) !important; }
.sc-m7-ok { fill: var(--success) !important; }
.sc-m7-dash { fill: none; stroke: var(--sc-line); stroke-width: 2.5; stroke-dasharray: 6 5; }
.sc-m7-line { fill: none; stroke: var(--sc-ink); stroke-width: 3; stroke-linecap: round; }
.sc-m7-rail { stroke: var(--sc-ink); stroke-width: 4; stroke-linecap: round; }
.sc-m7-sleeper { stroke: var(--sc-crust); stroke-width: 5; }
.sc-m7-road { stroke: var(--sc-soft); stroke-opacity: 0.3; stroke-width: 36; }
.sc-m7-lane { stroke: var(--sc-cream); stroke-width: 3; stroke-dasharray: 12 10; }
.sc-m7-grab { cursor: grab; touch-action: none; }
.sc-m7-grab:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.task.is-locked .sc-m7-grab { pointer-events: none; cursor: default; }
.sc-m7-dim { opacity: 0.25; }
.sc-m7-m { font-size: 19px; }
.sc-m7-dark { fill: #1c1a2e !important; }
.sc-m7-layer { stroke: var(--sc-line); stroke-width: 1.5; }

/* scenes: Russian grades 7–9 */
/* Scenes: Russian grades 7–9 (js/scenes-rus79.js) */
.sc-r79-rule { stroke: var(--sc-line); stroke-width: 1.2; }
.sc-r79-margin { stroke: var(--sc-red); stroke-width: 1.6; opacity: 0.45; }
.scene-fig .sc-r79-w { font-size: 18px; }
.scene-fig .sc-r79-big { font-size: 24px; }
.scene-fig .sc-r79-small { font-size: 15px; fill: var(--sc-soft); }
.scene-fig .sc-r79-tiny { font-size: 14px; }
.scene-fig .sc-r79-card { font-size: 15px; }
.scene-fig .sc-r79-fruit { font-size: 14px; }
.scene-fig .sc-r79-mag { font-size: 16px; fill: #fff; }
.scene-fig .sc-r79-mag.sc-r79-dark { fill: #1c1a2e; }
.scene-fig .sc-r79-mark { font-size: 24px; }
.scene-fig .sc-r79-on { font-size: 15px; fill: var(--sc-cream); }
.scene-fig .sc-r79-onfill { fill: #fff; }
.scene-fig .sc-r79-redtext { fill: var(--sc-red); }
.scene-fig .sc-r79-teal { fill: var(--sc-teal); }
.scene-fig .sc-r79-violet { fill: var(--sc-violet); }
.sc-r79-tile rect, .sc-r79-tilebg { fill: var(--sc-cream); stroke: var(--sc-ink); stroke-width: 2; }
.sc-r79-word { fill: var(--sc-cream); stroke: var(--sc-line); stroke-width: 2; }
.sc-r79-hl { fill: color-mix(in srgb, var(--sc-gold) 45%, transparent); }
.sc-r79-idiom { fill: color-mix(in srgb, var(--sc-gold) 55%, transparent); }
.sc-r79-hit { fill: transparent; }
.sc-zone.sc-r79-clear { fill: transparent; }
.sc-r79-glass { fill: color-mix(in srgb, var(--sc-blue) 32%, var(--sc-cream)); }
.sc-r79-seam { stroke: var(--sc-line); stroke-width: 2.5; }
.sc-r79-ne { transition: transform 220ms cubic-bezier(.2,.8,.2,1); }
.sc-r79-tool { fill: var(--sc-cream); stroke: var(--sc-line); stroke-width: 2; }
.sc-r79-tool.is-on { fill: color-mix(in srgb, var(--sc-teal) 22%, var(--sc-cream)); stroke: var(--sc-teal); stroke-width: 3; }
.sc-r79-under { stroke: var(--sc-red); stroke-width: 2.5; stroke-linecap: round; }
.sc-r79-ray { stroke: var(--sc-gold); stroke-width: 4; stroke-linecap: round; }
.sc-r79-bar { stroke: var(--sc-ink); stroke-width: 4; stroke-linecap: round; }
.sc-r79-arrow { fill: none; stroke: var(--sc-red); stroke-width: 3; stroke-linecap: round; }
.sc-r79-arrow.sc-r79-teal-stroke { stroke: var(--sc-teal); }
.sc-r79-leaf { fill: none; stroke: var(--sc-teal); stroke-width: 2.5; stroke-linecap: round; }
.sc-r79-reed { fill: none; stroke: var(--sc-teal); stroke-width: 3.5; stroke-linecap: round; }
.sc-r79-log { fill: none; stroke: var(--sc-crust); stroke-width: 9; stroke-linecap: round; }
.sc-r79-heard { filter: drop-shadow(0 0 5px var(--sc-gold)); }
.sc-r79-picked { filter: drop-shadow(0 0 4px var(--accent)) drop-shadow(0 0 2px var(--accent)); }
.sc-r79-choices { display: flex; flex-wrap: wrap; justify-content: center; margin: 0.5rem auto 0; max-width: 100%; }
.sc-r79-choices button { flex: 1 1 auto; min-height: 44px; }
@media (prefers-reduced-motion: reduce) { .sc-r79-ne { transition: none; } }
/* the sentences use the site's reading font: Unbounded is too wide for a sentence with mark slots */
.scene-fig .sc-r79-w, .scene-fig .sc-r79-big, .scene-fig .sc-r79-mag, .scene-fig .sc-r79-card, .scene-fig .sc-r79-fruit,
.scene-fig .sc-r79-small, .scene-fig .sc-r79-tiny, .scene-fig .sc-r79-on, .scene-fig .sc-r79-mark { font-family: "Onest", system-ui, sans-serif; font-weight: 700; }
.scene-fig .sc-r79-on.sc-r79-sm { font-size: 14px; }

/* scenes: grade 8 */
/* math8 scenes (js/scenes-math8.js) */
.sc-t14 { font-size: 14px; } .sc-t16 { font-size: 16px; } .sc-t18 { font-size: 18px; } .sc-t20 { font-size: 20px; } .sc-t22 { font-size: 22px; }
.sc-tx-teal { fill: var(--sc-teal) !important; } .sc-tx-red { fill: var(--sc-red) !important; } .sc-tx-gold { fill: var(--sc-gold) !important; }
.sc-tx-soft { fill: var(--sc-soft) !important; } .sc-tx-cream { fill: var(--sc-cream) !important; }
.sc-ln { fill: none; stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
.sc-ln-ink { stroke: var(--sc-ink); } .sc-ln-teal { stroke: var(--sc-teal); } .sc-ln-red { stroke: var(--sc-red); } .sc-ln-gold { stroke: var(--sc-gold); }
.sc-ln.sc-thin { stroke-width: 2; } .sc-ln.sc-thick { stroke-width: 6; }
.sc-dash { stroke-dasharray: 7 6; }
.sc-grid { stroke: var(--sc-line); stroke-width: 1.5; }
.sc-faint { opacity: 0.4; }
.sc-walk { fill: none; stroke: var(--sc-cheese); stroke-width: 7; stroke-linecap: round; stroke-linejoin: round; }
.sc-wood { fill: none; stroke: var(--sc-crust); stroke-width: 10; stroke-linejoin: round; stroke-linecap: round; }
.sc-goal { stroke: var(--sc-cream); stroke-width: 5; stroke-linecap: round; }
.sc-hit { fill: transparent; }
.sc-grip { cursor: grab; touch-action: none; }
.sc-grip:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.task.is-locked .sc-grip { cursor: default; pointer-events: none; }
.sc-slot { stroke: var(--sc-line); stroke-width: 2.5; stroke-dasharray: 6 5; }
.sc-card.is-on .sc-card-bg { fill: var(--sc-gold); }
.sc-tri { touch-action: none; }
.sc-card.is-on .sc-card-text { fill: #1c1a2e !important; }

/* Sign in with Google (js/auth.js) */
.auth-box {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem 0.75rem;
  margin-bottom: 1rem;
  padding-bottom: 1rem;
  border-bottom: 1px dashed var(--border);
}
.auth-google.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  background: #ffffff;
  color: #1f1f1f;
  border: 1px solid #747775;
  box-shadow: none;
}
.auth-google.btn:hover { background: #f4f6fa; }
.auth-google:disabled { opacity: 0.6; cursor: progress; }
:root[data-theme="dark"] .auth-google.btn { background: #131314; color: #e3e3e3; border-color: #8e918f; }
:root[data-theme="dark"] .auth-google.btn:hover { background: #1f1f20; }
.auth-note, .auth-who { flex: 1 1 14rem; margin: 0; font-size: 0.88rem; color: var(--soft); }
.auth-who strong { color: var(--ink); overflow-wrap: anywhere; }