:root {
  color-scheme: light;
  --paper: #f2f6fc;
  --surface: #ffffff;
  --surface-raised: #f8faff;
  --surface-inset: #eaf1fa;
  --surface-pressed: #dceaf8;
  --ink: #202d44;
  --muted: #52637c;
  --forest: #152740;
  --line: #d0dbe9;
  --control-line: #8094ad;
  --accent-text: #145785;
  --accent-fill: #17639a;
  --accent-hover: #0f4d7c;
  --accent-on-fill: #ffffff;
  --accent-soft: #e0effc;
  --accent-border: #90b2d0;
  --success-fill: #e3f3ec;
  --success-line: #59987d;
  --success-ink: #1e624a;
  --error-fill: #fae9ed;
  --error-line: #ad6677;
  --danger: #94384e;
  --warning-fill: #fcf0d9;
  --warning-line: #c5944b;
  --warning-ink: #79561b;
  --hero-bg: #102847;
  --hero-ink: #f2f8ff;
  --hero-muted: #c5d7ed;
  --hero-accent: #98dcff;
  --hero-image-tone: #37628e;
  --shadow-color: #172a421a;
  --overlay-color: #08101db3;
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --paper: #0d1524;
  --surface: #141f33;
  --surface-raised: #19263c;
  --surface-inset: #101b2d;
  --surface-pressed: #233750;
  --ink: #e5eef9;
  --muted: #a9bad0;
  --forest: #f0f6ff;
  --line: #2a3b55;
  --control-line: #5e7492;
  --accent-text: #8bd7fb;
  --accent-fill: #88d5fb;
  --accent-hover: #b3e5ff;
  --accent-on-fill: #0e2940;
  --accent-soft: #1b334c;
  --accent-border: #4f779a;
  --success-fill: #16382f;
  --success-line: #438f74;
  --success-ink: #9ce1c0;
  --error-fill: #422634;
  --error-line: #9d5e73;
  --danger: #ffb5c4;
  --warning-fill: #3d3023;
  --warning-line: #967249;
  --warning-ink: #f7d7a3;
  --hero-bg: #102541;
  --hero-image-tone: #2a4b73;
  --shadow-color: #050a1459;
  --overlay-color: #050915c7;
}

::selection { color: var(--accent-on-fill); background: var(--accent-fill); }
:focus-visible { outline-color: var(--accent-text); }
.skip-link { color: var(--accent-text); }
.page:focus { outline: none; }
.page:focus-visible :is(.view-head, .hero-copy) h1 {
  inline-size: fit-content;
  border-radius: 3px;
  outline: 2px solid var(--accent-text);
  outline-offset: 5px;
}

.page:focus-visible .hero-copy h1 { outline-color: var(--hero-accent); }

.sidebar {
  background: var(--surface-inset);
  border-color: var(--line);
}

.brand-mark {
  background: var(--hero-bg);
  color: var(--hero-accent);
}

[data-theme="dark"] .brand-mark {
  background: var(--accent-soft);
  border: 1px solid var(--accent-border);
}

.sidebar-bottom { border-color: var(--line); }
.sidebar-bottom svg { color: var(--success-ink); }

.nav-link[aria-current="page"] {
  background: var(--accent-soft);
  color: var(--accent-text);
}
.nav-link:hover { background: var(--surface-pressed); }
.nav-link[aria-current="page"]:hover { background: var(--accent-soft); color: var(--accent-text); }

.language-switch { background: var(--surface-inset); }
.language-switch :is(button, a):is(.active, .is-active, [aria-pressed="true"], [aria-current="true"]) {
  background: var(--surface-raised);
  color: var(--accent-text);
  box-shadow: 0 1px 2px var(--shadow-color);
}

.pill {
  border-color: var(--line);
  background: var(--surface-inset);
  color: var(--accent-text);
}

.hero {
  min-block-size: 348px;
  border: 1px solid #304a69;
  background: var(--hero-bg);
  color: var(--hero-ink);
}

.hero-copy { position: relative; z-index: 1; }
.eyebrow { color: var(--accent-text); }
.hero .eyebrow, .hero h1 em { color: var(--hero-accent); }
.hero-copy > p:not(.eyebrow) { color: var(--hero-muted); }
.hero .pill { border-color: #6382a2; color: var(--hero-ink); }
.hero a:focus-visible, .hero button:focus-visible { outline-color: var(--hero-accent); }
.hero-image { background: var(--hero-image-tone); }

.hero-image img {
  opacity: .82;
  filter: grayscale(1) contrast(.9);
  mix-blend-mode: luminosity;
}

.hero-image::after {
  position: absolute;
  inset: 0;
  box-shadow: inset 0 0 0 1px #ffffff12;
  content: "";
  pointer-events: none;
}

.hero-image figcaption { background: var(--surface-raised); color: var(--forest); }

.btn, .tab, .quiz-option { min-block-size: 44px; }
.btn-primary { background: var(--accent-fill); color: var(--accent-on-fill); }
.btn-primary:hover:not(:disabled) { background: var(--accent-hover); }
.btn-light { background: var(--hero-accent); color: #102842; }
.btn-light:hover:not(:disabled) { background: #c8edff; }
.btn-ghost { border-color: var(--control-line); }
.hero .btn-ghost {
  border-color: #829cb9;
  background: #112846;
  color: var(--hero-ink);
}

.tile-icon:is(.mint, .sand, .blue, .rose) {
  background: var(--accent-soft);
  color: var(--accent-text);
}

.tile-arrow { color: var(--accent-text); }
.plan { background: var(--surface-raised); }
.plan-item + .plan-item { border-color: var(--line); }
.plan-num { background: var(--accent-soft); color: var(--accent-text); }
.home-exam > p { color: var(--muted); }
.progress-track { background: var(--surface-pressed); }
.progress-fill { background: var(--accent-fill); }

.tab:is(.active, .is-active, [aria-selected="true"], [aria-pressed="true"], [aria-current="page"]),
.step-link:is(.active, .is-active, [aria-current="step"], [aria-pressed="true"]) {
  border-color: var(--accent-border);
  background: var(--accent-soft);
  color: var(--accent-text);
}

select, input:not([type="checkbox"], [type="radio"]), textarea {
  border-color: var(--control-line);
  background: var(--surface-inset);
  color: var(--ink);
}

textarea::placeholder, input::placeholder { color: var(--muted); opacity: 1; }

.callout, .feedback, .empty {
  border-color: var(--accent-border);
  background: var(--accent-soft);
  color: var(--forest);
}

.feedback.success,
.quiz-option:is(.correct, [data-state="correct"]) {
  border-color: var(--success-line);
  background: var(--success-fill);
  color: var(--success-ink);
}

.feedback:is(.error, .incorrect, [data-state="incorrect"]),
.quiz-option:is(.incorrect, [data-state="incorrect"]) {
  border-color: var(--error-line);
  background: var(--error-fill);
  color: var(--danger);
}

.source-text, .example-text {
  border-color: var(--accent-border);
  background: var(--surface-inset);
  color: var(--ink);
}

.step::marker, .signal-list li::marker { color: var(--accent-text); }
.phrase { border-color: var(--line); background: var(--surface-raised); }
.compare > *, .result-text { background: var(--surface-inset); }
.compare > :nth-child(2) { background: var(--accent-soft); }
.flip-face { border-color: var(--accent-border); background: var(--accent-soft); }
.flip-back { border-color: var(--line); background: var(--surface-raised); }
.quiz-option:is(.selected, .is-selected, [aria-pressed="true"]):not(.correct, .incorrect) {
  border-color: var(--accent-border);
  background: var(--accent-soft);
}

.checklist input { accent-color: var(--accent-fill); }
.timer { border-color: var(--warning-line); background: var(--warning-fill); color: var(--warning-ink); }
.status-dot { background: var(--success-ink); }
.finish-result { border-color: var(--line); background: var(--surface-inset); }
.success-toast {
  border-color: var(--success-line);
  background: var(--success-fill);
  color: var(--success-ink);
  box-shadow: 0 5px 22px var(--shadow-color);
}

.success-toast svg { color: currentColor; }
.marker, .result-text mark { background: var(--warning-fill); color: var(--warning-ink); }
.marker:is(.error, .incorrect), .result-text mark:is(.error, .incorrect) {
  background: var(--error-fill);
  color: var(--danger);
}

.tag { background: var(--accent-soft); color: var(--accent-text); }

.appearance-picker, .choice-trigger {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  max-inline-size: 100%;
  min-block-size: 44px;
  padding: 7px 11px;
  border: 1px solid var(--control-line);
  border-radius: 10px;
  background: var(--surface);
  color: var(--ink);
  font-size: .86rem;
  font-weight: 650;
  text-align: start;
}

.appearance-picker { min-inline-size: 44px; padding-inline: 9px; }
.appearance-picker svg, .choice-trigger svg { inline-size: 17px; block-size: 17px; }
.choice-trigger[aria-expanded="true"] {
  border-color: var(--accent-border);
  background: var(--accent-soft);
  color: var(--accent-text);
}

.choice-sheet {
  inline-size: min(460px, calc(100% - 32px));
  max-inline-size: none;
  max-block-size: calc(100dvh - 32px);
  padding: 0;
  border: 0;
  overflow: visible;
  background: transparent;
  color: var(--ink);
}

.choice-sheet::backdrop { background: var(--overlay-color); }
.choice-content {
  max-block-size: calc(100dvh - 32px);
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: 20px;
  overflow-y: auto;
  overscroll-behavior: contain;
  background: var(--surface);
  box-shadow: 0 22px 72px var(--shadow-color);
}

.choice-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-block-end: 12px;
}

.choice-heading h2 { font-size: 1.2rem; }
.choice-options {
  display: grid;
  gap: 6px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.choice-option {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  inline-size: 100%;
  min-block-size: 48px;
  padding: 9px 13px;
  border: 1px solid transparent;
  border-radius: 10px;
  background: var(--surface-inset);
  color: var(--ink);
  font-size: .93rem;
  font-weight: 620;
  text-align: start;
}

.choice-option:is([aria-checked="true"], [aria-pressed="true"], [data-selected="true"], .is-selected) {
  border-color: var(--accent-border);
  background: var(--accent-soft);
  color: var(--accent-text);
}

.choice-option svg { inline-size: 17px; block-size: 17px; }

.mode-grid, .shortcut-grid, .learning-index {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 185px), 1fr));
  gap: 11px;
}

.mode-card {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: 12px;
  inline-size: 100%;
  min-block-size: 68px;
  padding: 13px;
  border: 1px solid var(--line);
  border-radius: 13px;
  background: var(--surface);
  color: var(--forest);
  text-align: start;
  text-decoration: none;
}

.mode-card strong { display: block; font-size: 1rem; }
.mode-card h2 { font-size: 1.04rem; font-weight: 720; }
.mode-card :is(small, p) { display: block; color: var(--muted); font-size: .82rem; }
.mode-card .tile-arrow { grid-area: auto; margin: 0; }
.mode-card > svg { inline-size: 19px; block-size: 19px; color: var(--accent-text); }

.hero .mode-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.hero .mode-card { border-color: #557395; background: #1a3557; color: var(--hero-ink); }
.hero .mode-card :is(small, p) { color: var(--hero-muted); }
.hero .mode-card :is(.tile-arrow, svg) { color: var(--hero-accent); }
.hero .mode-card .tile-icon { background: #294c71; }

.learning-tabs, .practice-switch, .topic-nav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 7px;
}

.learning-tabs, .practice-switch { margin-block-end: 16px; }
.learning-index { grid-template-columns: minmax(0, 1fr); }
.topic-nav { margin-block-end: 11px; }
.topic-nav > *, .step-nav > * { min-block-size: 44px; }
.study-tip {
  padding: 15px;
  border: 1px solid var(--line);
  border-radius: 13px;
  background: var(--surface-raised);
}

.study-tip > * + * { margin-block-start: 8px; }
.study-tip h3 { font-size: 1rem; }
.study-tip .compare p { white-space: pre-wrap; }
.study-tip summary .plan-num {
  display: inline-grid;
  inline-size: 26px;
  min-block-size: 26px;
  margin-inline-end: 7px;
  vertical-align: middle;
}

.study-tip summary small { color: var(--muted); }
.step-nav { align-items: center; }
.step-link { font-variant-numeric: tabular-nums; }

.btn-ghost:hover:not(:disabled), .tab:hover, .quiz-option:hover:not(:disabled),
.step-link:hover, button.phrase:hover, .board-item:is(button, a):hover {
  border-color: var(--accent-border);
  background: var(--surface-pressed);
}

.tab:is([aria-pressed="true"], [aria-current="page"]):hover, .step-link[aria-current="step"]:hover { background: var(--accent-soft); }
.tile:hover { border-color: var(--accent-border); box-shadow: 0 9px 20px var(--shadow-color); }
:is(a, button).plan-item:hover { color: var(--accent-text); }

@media (hover: hover) {
  .choice-option:hover, .choice-trigger:hover, .appearance-picker:hover, .mode-card:hover {
    border-color: var(--accent-border);
    background: var(--surface-pressed);
  }
  .hero .btn-ghost:hover:not(:disabled), .hero .mode-card:hover { border-color: #9bc3e3; background: #234468; }
  .choice-option[aria-checked="true"]:hover, .choice-option[aria-pressed="true"]:hover { background: var(--accent-soft); }
}

@media (hover: none) {
  .nav-link:not([aria-current="page"]):hover { background: transparent; color: var(--muted); }
  .btn-primary:hover:not(:disabled) { background: var(--accent-fill); }
  .btn-light:hover:not(:disabled) { background: var(--hero-accent); }
  .btn-ghost:hover:not(:disabled) { border-color: var(--control-line); background: var(--surface); }
  .hero .btn-ghost:hover:not(:disabled) { border-color: #829cb9; background: #112846; }
  .tab:not([aria-pressed="true"], [aria-current="page"]):hover, .quiz-option:hover:not(:disabled),
  .step-link:not([aria-current="step"]):hover, .board-item:is(button, a):hover {
    border-color: var(--line);
    background: var(--surface);
  }
  button.phrase:hover { background: var(--surface-raised); }
  .tile:hover { border-color: var(--line); box-shadow: none; }
  :is(a, button).plan-item:hover { color: var(--forest); }
}

@media (max-width: 850px) {
  .nav { background: var(--surface); border-color: var(--line); box-shadow: 0 -5px 20px var(--shadow-color); }
  .nav:has(> :nth-child(5)) { grid-template-columns: repeat(5, minmax(0, 1fr)); }
  .nav-link { font-size: clamp(.62rem, 2.3vw, .76rem); }
}

@media (max-width: 1050px) {
  .mode-card { grid-template-columns: auto minmax(0, 1fr); gap: 6px 8px; padding: 10px; }
  .mode-card > span:nth-child(2) { display: contents; }
  .mode-card > :is(.tile-arrow, svg):last-child { display: none; }
  .mode-card .tile-icon { inline-size: 30px; block-size: 30px; }
  .mode-card .tile-icon svg { inline-size: 16px; block-size: 16px; }
  .mode-card :is(strong, h2) { font-size: .91rem; }
  .mode-card :is(small, p) { grid-column: 1 / -1; font-size: .76rem; }
}

@media (max-width: 570px) {
  .topbar { min-block-size: 57px; }
  .language-switch :is(button, a) { min-inline-size: 34px; min-block-size: 38px; }
  .top-meta .pill { display: none; }
  .hero { min-block-size: 0; }
  .hero-copy { padding: 22px 19px; }
  .hero h1 { max-inline-size: 16ch; font-size: clamp(2.15rem, 8.4vw, 3.15rem); }
  .hero-image {
    position: absolute;
    inset-block: 0;
    inset-inline: auto 0;
    inline-size: min(50%, 200px);
    opacity: .26;
    mask-image: linear-gradient(90deg, transparent, black 75%);
  }
  .hero .mode-grid { gap: 8px; }
  .choice-sheet {
    inset-block: auto 0;
    inset-inline: 0;
    inline-size: 100%;
    margin: 0;
  }
  .choice-content {
    max-block-size: calc(100dvh - 20px);
    padding: 16px max(15px, env(safe-area-inset-right)) max(16px, env(safe-area-inset-bottom)) max(15px, env(safe-area-inset-left));
    border-end-start-radius: 0;
    border-end-end-radius: 0;
  }
  .learning-tabs, .practice-switch, .topic-nav { gap: 5px; }
  .step-nav {
    display: grid;
    grid-template-columns: repeat(6, minmax(0, 1fr));
    gap: 5px;
  }
  .step-link { justify-content: center; }
  .step-name { display: none; }
}