/* Teaching app — responsive aurora study desk with light/dark themes. */
:root {
  color-scheme: light;
  --bg: #f3f6ff;
  --fg: #182038;
  --muted: #5d6780;
  --accent: #315fe8;
  --accent-strong: #2048c7;
  --accent-soft: #e9efff;
  --surface: rgba(255, 255, 255, 0.82);
  --surface-solid: #fff;
  --surface-muted: #f7f9ff;
  --surface-hover: #f0f4ff;
  --border: #d5dcef;
  --border-strong: #b8c5e4;
  --code-bg: #eef2fb;
  --good: #157347;
  --good-soft: #e7f7ee;
  --bad: #bd2c3b;
  --bad-soft: #fdecef;
  --warning: #805b00;
  --warning-soft: #fff6d8;
  --star: #d99000;
  --shadow-sm: 0 6px 18px rgba(49, 70, 125, 0.08);
  --shadow-md: 0 18px 45px rgba(49, 70, 125, 0.13);
  --backdrop: blur(18px) saturate(1.15);
  --page-background:
    radial-gradient(circle at 8% 4%, rgba(89, 126, 247, 0.18), transparent 27rem),
    radial-gradient(circle at 92% 12%, rgba(142, 90, 235, 0.14), transparent 25rem),
    linear-gradient(rgba(82, 103, 163, 0.045) 1px, transparent 1px),
    linear-gradient(90deg, rgba(82, 103, 163, 0.045) 1px, transparent 1px);
  --mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #09101f;
  --fg: #e7ecf8;
  --muted: #a4aec4;
  --accent: #8badff;
  --accent-strong: #acc4ff;
  --accent-soft: #18294e;
  --surface: rgba(15, 24, 44, 0.84);
  --surface-solid: #111b31;
  --surface-muted: #141f37;
  --surface-hover: #1a2947;
  --border: #2b3855;
  --border-strong: #405171;
  --code-bg: #121c30;
  --good: #68dfa0;
  --good-soft: #123625;
  --bad: #ff8d9d;
  --bad-soft: #421d28;
  --warning: #ffd875;
  --warning-soft: #3b3016;
  --star: #ffc857;
  --shadow-sm: 0 8px 22px rgba(0, 0, 0, 0.25);
  --shadow-md: 0 22px 55px rgba(0, 0, 0, 0.38);
  --page-background:
    radial-gradient(circle at 8% 4%, rgba(67, 98, 205, 0.27), transparent 29rem),
    radial-gradient(circle at 92% 12%, rgba(111, 65, 186, 0.22), transparent 27rem),
    linear-gradient(rgba(155, 173, 220, 0.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(155, 173, 220, 0.035) 1px, transparent 1px);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    color-scheme: dark;
    --bg: #09101f;
    --fg: #e7ecf8;
    --muted: #a4aec4;
    --accent: #8badff;
    --accent-strong: #acc4ff;
    --accent-soft: #18294e;
    --surface: rgba(15, 24, 44, 0.84);
    --surface-solid: #111b31;
    --surface-muted: #141f37;
    --surface-hover: #1a2947;
    --border: #2b3855;
    --border-strong: #405171;
    --code-bg: #121c30;
    --good: #68dfa0;
    --good-soft: #123625;
    --bad: #ff8d9d;
    --bad-soft: #421d28;
    --warning: #ffd875;
    --warning-soft: #3b3016;
    --star: #ffc857;
    --shadow-sm: 0 8px 22px rgba(0, 0, 0, 0.25);
    --shadow-md: 0 22px 55px rgba(0, 0, 0, 0.38);
    --page-background:
      radial-gradient(circle at 8% 4%, rgba(67, 98, 205, 0.27), transparent 29rem),
      radial-gradient(circle at 92% 12%, rgba(111, 65, 186, 0.22), transparent 27rem),
      linear-gradient(rgba(155, 173, 220, 0.035) 1px, transparent 1px),
      linear-gradient(90deg, rgba(155, 173, 220, 0.035) 1px, transparent 1px);
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  min-height: 100vh;
  background-color: var(--bg);
  background-image: var(--page-background);
  background-size: auto, auto, 32px 32px, 32px 32px;
  background-attachment: fixed;
  color: var(--fg);
  line-height: 1.55;
  transition: background-color 180ms ease, color 180ms ease;
}

header.site {
  padding: 1.2rem 1.5rem 0.6rem;
  border-bottom: 1px solid var(--border);
}
header.site h1 { margin: 0 0 0.2rem; font-size: 1.4rem; }
header.site .sub { color: var(--muted); font-size: 0.9rem; }

main { max-width: 980px; margin: 0 auto; padding: 1.2rem 1.5rem 4rem; }

/* Tabs */
.tabs { display: flex; gap: 0.4rem; flex-wrap: wrap; margin: 1rem 0 0.8rem; }
.tabs button {
  font: inherit;
  padding: 0.45rem 0.9rem;
  border: 1px solid var(--border);
  background: var(--surface-solid);
  border-radius: 6px;
  cursor: pointer;
}
.tabs button.active { background: var(--accent); color: #fff; border-color: var(--accent); }

/* Search */
#search {
  width: 100%;
  font: inherit;
  padding: 0.5rem 0.7rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  margin-bottom: 1rem;
}

/* Problem list */
.prob-list { list-style: none; margin: 0; padding: 0; }
.prob-row {
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
  padding: 0.6rem 0.4rem;
  border-bottom: 1px solid var(--border);
}
.prob-row .title { font-weight: 600; flex: 1; }
.prob-row .star { color: var(--star); }
.prob-row .reports { color: var(--muted); font-size: 0.85rem; white-space: nowrap; }
.prob-row .links a { margin-left: 0.6rem; font-size: 0.85rem; }
.prob-row .concept { color: var(--muted); font-size: 0.85rem; }

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.company-actions { margin: 0.8rem 0; font-size: 0.9rem; }
.company-actions a { margin-right: 1rem; }

/* Code blocks (monospace) */
pre, code { font-family: var(--mono); }
pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.9rem;
  overflow-x: auto;
  font-size: 0.82rem;
  line-height: 1.45;
}
code { font-size: 0.85em; }
p code, li code { background: var(--code-bg); padding: 0.05rem 0.3rem; border-radius: 4px; }

/* Reference page sections */
section.ref { margin: 1.4rem 0; }
section.ref h2 { border-bottom: 1px solid var(--border); padding-bottom: 0.25rem; }

/* Visualization widget */
.viz {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem;
  background: var(--surface);
}
.viz-frame { min-height: 5rem; margin-bottom: 0.7rem; }
.viz-controls { display: flex; align-items: center; gap: 0.7rem; }
.viz-controls button {
  font: inherit; padding: 0.35rem 0.8rem; border: 1px solid var(--border);
  background: var(--surface-solid); color: var(--fg); border-radius: 6px; cursor: pointer;
}
.viz-counter { color: var(--muted); font-size: 0.85rem; }
.viz-empty { color: var(--muted); font-style: italic; }

/* Deck slides */
.deck { max-width: 760px; margin: 1.5rem auto; }
section.slide {
  display: none;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1.5rem;
  background: var(--surface);
  min-height: 18rem;
}
section.slide.active { display: block; }
section.slide h2 { margin-top: 0; }
.deck-nav { display: flex; align-items: center; gap: 1rem; margin-top: 1rem; }
.deck-nav button {
  font: inherit; padding: 0.4rem 0.9rem; border: 1px solid var(--border);
  background: var(--surface-solid); color: var(--fg); border-radius: 6px; cursor: pointer;
}
.deck-counter { color: var(--muted); font-size: 0.9rem; }
.deck-footer { margin-top: 1rem; font-size: 0.9rem; }
.deck-footer a { margin-right: 1rem; }

/* Quiz cards */
.quiz-card {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem 1.2rem;
  background: var(--surface);
  margin-bottom: 1rem;
}
.quiz-card .qmeta { font-size: 0.8rem; color: var(--muted); margin-bottom: 0.4rem; }
.quiz-card .qprompt { font-weight: 600; margin-bottom: 0.6rem; white-space: pre-wrap; }
.quiz-card label { display: block; margin: 0.25rem 0; cursor: pointer; }
.quiz-card .qinput { width: 100%; font: inherit; padding: 0.4rem; border: 1px solid var(--border); border-radius: 6px; }
.quiz-card button.check {
  font: inherit; margin-top: 0.6rem; padding: 0.4rem 0.9rem;
  border: 1px solid var(--accent); background: var(--accent); color: #fff;
  border-radius: 6px; cursor: pointer;
}
.quiz-card .feedback { margin-top: 0.7rem; padding: 0.6rem; border-radius: 6px; display: none; }
.quiz-card .feedback.show { display: block; }
.quiz-card .feedback.right { background: var(--good-soft); color: var(--good); }
.quiz-card .feedback.wrong { background: var(--bad-soft); color: var(--bad); }
.quiz-card .feedback a { display: inline-block; margin-top: 0.3rem; }

#score {
  position: sticky; top: 0; background: var(--accent-soft);
  border: 1px solid var(--accent); border-radius: 6px;
  padding: 0.5rem 0.9rem; margin-bottom: 1rem; font-weight: 600;
  z-index: 5;
}

.empty-state { color: var(--muted); font-style: italic; padding: 1rem; }

/* Shared polish and learning UX */
body { overflow-wrap: anywhere; }

h1, h2, h3 { line-height: 1.2; }
h2 { margin-top: 2rem; }

button, input, select { min-height: 2.5rem; }
button { touch-action: manipulation; }
button:focus-visible, input:focus-visible, select:focus-visible,
a:focus-visible, summary:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--accent) 55%, white);
  outline-offset: 2px;
}

body > .page-head {
  max-width: 980px;
  margin: 0 auto;
  padding: 1.5rem 1.5rem 0;
}
.page-head { margin-bottom: 1.5rem; }
.page-head h1 { margin: 0.45rem 0 0.75rem; }
.page-head .crumb, .page-head .links, .page-head .page-links {
  color: var(--muted);
}
.page-head .btn, .page-links a, .links a {
  display: inline-block;
  margin: 0.15rem 0.45rem 0.15rem 0;
}

main.page > section, main.prose > section, main.reference > section,
main.page-body > section {
  max-width: 78ch;
}

/* Long reference code is progressive disclosure, with copy/expand controls. */
.code-shell { position: relative; }
.code-toolbar {
  display: flex;
  justify-content: flex-end;
  gap: 0.5rem;
  margin: 0.45rem 0;
}
.code-toolbar button, .recall-actions button, .self-grade button,
.deck-steps button {
  font: inherit;
  border: 1px solid var(--border);
  background: var(--surface-solid);
  color: var(--fg);
  border-radius: 999px;
  padding: 0.35rem 0.8rem;
  cursor: pointer;
}
.code-shell.collapsed pre { max-height: 22rem; }
.code-shell.collapsed::after {
  content: "";
  position: absolute;
  pointer-events: none;
  left: 0;
  right: 0;
  bottom: 0;
  height: 4rem;
  background: linear-gradient(transparent, var(--surface-solid));
}

/* Quick recall: reveal from memory first, then self-grade for later review. */
.recall-panel {
  max-width: 78ch;
  border: 1px solid var(--border-strong);
  border-radius: 10px;
  padding: 1rem 1.1rem;
  margin: 1rem 0 1.8rem;
  background: linear-gradient(135deg, var(--accent-soft), var(--surface));
}
.recall-panel h2 { margin: 0 0 0.25rem; font-size: 1.15rem; }
.recall-panel > p { margin: 0 0 0.75rem; color: var(--muted); }
.recall-panel details {
  border-top: 1px solid var(--border);
  padding: 0.55rem 0;
}
.recall-panel summary { cursor: pointer; font-weight: 650; }
.recall-panel details p { margin: 0.55rem 0 0.15rem; }
.recall-actions {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin-top: 0.75rem;
}
.recall-actions .again { border-color: #ef9a9a; }
.recall-actions .hard { border-color: #f4c86b; }
.recall-actions .good { border-color: #81c995; }
.recall-status { color: var(--muted); font-size: 0.85rem; }

/* SVGs stay readable: on narrow screens, scroll rather than shrink 10px text. */
.visualization-scene {
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--surface-solid);
  margin: 0.8rem 0 1.4rem;
  overflow: hidden;
}
.scene-label {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.5rem 0.75rem;
  border-bottom: 1px solid var(--border);
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.02em;
}
.scene-label.positive { color: var(--good); background: var(--good-soft); }
.scene-label.negative { color: var(--bad); background: var(--bad-soft); }
.svg-scroll { overflow-x: auto; overscroll-behavior-inline: contain; background: #fff; }
.svg-scroll > svg { display: block; width: 100%; }
.scroll-hint { display: none; }

/* Step-through visualization */
.viz { margin: 1.5rem 0; max-width: 78ch; }
.viz-heading { margin: 0 0 0.2rem; font-size: 1.1rem; }
.viz-prompt { margin: 0 0 0.8rem; color: var(--muted); font-size: 0.9rem; }
.viz-frame {
  min-height: 8rem;
  padding: 0.9rem;
  border: 1px solid var(--border);
  border-radius: 7px;
  background: var(--surface-muted);
}
.viz-frame h3 { margin: 0 0 0.45rem; font-size: 1rem; }
.viz-controls { margin-top: 0.75rem; flex-wrap: wrap; }
.viz-controls button:disabled { opacity: 0.45; cursor: not-allowed; }
.viz-progress { width: min(15rem, 100%); height: 0.45rem; accent-color: var(--accent); }
.bar { display: flex; gap: 0.45rem; flex-wrap: wrap; margin: 0.65rem 0; }
.bar span, .ok, .hit, .bad, .gone {
  display: inline-block;
  border-radius: 5px;
  padding: 0.18rem 0.45rem;
}
.bar .ok, .ok, .hit { color: var(--good); background: var(--good-soft); }
.bar .bad, .bad { color: var(--bad); background: var(--bad-soft); }
.bar .gone, .gone { color: var(--muted); background: var(--surface-hover); text-decoration: line-through; }
.muted, .dim { color: var(--muted); }

/* Deck: explicit path, progress, and stable controls across heterogeneous pages. */
body.deck { width: min(100% - 2rem, 760px); padding: 0; }
.deck-head { margin-bottom: 1rem; }
.deck-head h1 { margin-bottom: 0.2rem; }
.deck-steps {
  display: flex;
  gap: 0.35rem;
  overflow-x: auto;
  margin: 0 0 0.75rem;
  padding: 0.15rem 0 0.4rem;
}
.deck-steps button { white-space: nowrap; font-size: 0.78rem; min-height: 2rem; }
.deck-steps button.active {
  color: #fff;
  background: var(--accent);
  border-color: var(--accent);
}
.deck-progress { width: 100%; height: 0.45rem; accent-color: var(--accent); }
.deck-nav, .deck-foot, .deck-footer {
  max-width: 760px;
  margin: 0.8rem auto 0;
}
.deck-foot button, .deck-footer button {
  font: inherit;
  padding: 0.4rem 0.9rem;
  border: 1px solid var(--border);
  background: var(--surface-solid);
  color: var(--fg);
  border-radius: 6px;
  cursor: pointer;
}
.deck-foot nav, .deck-footer nav { margin-top: 0.6rem; }
.recall-cue {
  color: var(--warning);
  background: var(--warning-soft);
  border-left: 4px solid var(--star);
  padding: 0.55rem 0.7rem;
  margin: 0 0 0.85rem;
}
.deck-grade { margin-top: 1rem; border-top: 1px solid var(--border); padding-top: 0.8rem; }

/* Index review status */
.study-status {
  flex: 0 0 auto;
  border-radius: 999px;
  padding: 0.12rem 0.45rem;
  font-size: 0.75rem;
  border: 1px solid var(--border);
  color: var(--muted);
  background: var(--surface-solid);
}
.study-status.due { color: var(--warning); border-color: var(--star); background: var(--warning-soft); }
.study-status.scheduled { color: var(--good); border-color: var(--good); background: var(--good-soft); }

/* Quiz: active-recall answer reveal and self-grading. */
.quiz-card fieldset { border: 0; margin: 0; padding: 0; }
.quiz-card legend { font-weight: 600; margin-bottom: 0.6rem; }
.quiz-card .qinput { min-height: 5.5rem; resize: vertical; }
.quiz-card button.reveal { background: var(--surface-solid); color: var(--accent); }
.self-grade { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 0.65rem; }
.self-grade .yes { border-color: #81c995; }
.self-grade .no { border-color: #ef9a9a; }
.quiz-card.answered { border-color: #b8c9ee; }

@media (max-width: 720px) {
  main { padding: 1rem 1rem 3rem; }
  body > .page-head { padding: 1rem 1rem 0; }
  header.site { padding-inline: 1rem; }
  h1 { font-size: 1.75rem; }
  h2 { font-size: 1.3rem; }

  .prob-row { align-items: center; flex-wrap: wrap; gap: 0.35rem 0.55rem; }
  .prob-row .title { flex-basis: calc(100% - 2rem); }
  .prob-row .concept { display: block; margin-top: 0.15rem; }
  .prob-row .reports { margin-left: 1.65rem; }
  .prob-row .links { margin-left: auto; }
  .prob-row .links a { display: inline-block; padding: 0.35rem 0; }

  .svg-scroll > svg { width: 620px !important; max-width: none !important; }
  .scroll-hint {
    display: block;
    margin: 0;
    padding: 0.35rem 0.75rem;
    color: var(--muted);
    border-top: 1px solid var(--border);
    font-size: 0.75rem;
  }

  section.slide { padding: 1rem; min-height: 0; }
  .deck-foot, .deck-footer, .deck-nav { position: sticky; bottom: 0; background: var(--bg); padding: 0.6rem 0; }
  .viz-controls { gap: 0.45rem; }
  .viz-progress { order: 4; flex-basis: 100%; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; }
}

/* Aurora layout system */
::selection { background: var(--accent); color: #fff; }

a { color: var(--accent); font-weight: 550; }
a:hover { color: var(--accent-strong); }

button, input, textarea, select { color: var(--fg); }
button, .prob-row, .quiz-card, section.slide, .recall-panel,
.visualization-scene, .page-head {
  transition: border-color 160ms ease, box-shadow 160ms ease,
    background-color 160ms ease, transform 160ms ease;
}
button:hover:not(:disabled) { border-color: var(--accent); }

.theme-toggle {
  position: fixed;
  z-index: 50;
  top: 0.8rem;
  right: 0.8rem;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  min-height: 2.35rem;
  padding: 0.38rem 0.7rem;
  color: var(--fg);
  background: var(--surface);
  border: 1px solid var(--border-strong);
  border-radius: 999px;
  box-shadow: var(--shadow-sm);
  backdrop-filter: var(--backdrop);
  -webkit-backdrop-filter: var(--backdrop);
  cursor: pointer;
  font: 650 0.78rem/1 system-ui, sans-serif;
}
.theme-toggle:hover { transform: translateY(-1px); box-shadow: var(--shadow-md); }
.theme-toggle span[aria-hidden] { font-size: 1rem; }

header.site {
  position: relative;
  padding: 2rem max(1.25rem, calc((100vw - 1120px) / 2)) 1.5rem;
  color: var(--fg);
  background: linear-gradient(120deg, var(--surface), color-mix(in srgb, var(--accent-soft) 72%, transparent));
  border-bottom: 1px solid var(--border-strong);
  box-shadow: var(--shadow-sm);
  backdrop-filter: var(--backdrop);
  -webkit-backdrop-filter: var(--backdrop);
}
header.site h1 {
  font-size: clamp(1.55rem, 3vw, 2.15rem);
  letter-spacing: -0.035em;
}
header.site .sub { max-width: 70ch; font-size: 0.95rem; }

main { max-width: 1000px; }
.site + main { max-width: 1120px; padding-top: 1.7rem; }

.tabs {
  gap: 0.55rem;
  margin-top: 0;
  padding: 0.3rem;
  width: fit-content;
  max-width: 100%;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  box-shadow: var(--shadow-sm);
  backdrop-filter: var(--backdrop);
  -webkit-backdrop-filter: var(--backdrop);
}
.tabs button {
  border-color: transparent;
  border-radius: 9px;
  padding: 0.5rem 1rem;
}
.tabs button.active {
  background: linear-gradient(135deg, var(--accent), var(--accent-strong));
  box-shadow: 0 7px 18px color-mix(in srgb, var(--accent) 28%, transparent);
}

#search, .quiz-card .qinput {
  background: var(--surface);
  border-color: var(--border-strong);
  box-shadow: inset 0 1px 0 color-mix(in srgb, white 55%, transparent), var(--shadow-sm);
}
#search {
  min-height: 3.15rem;
  padding-inline: 1rem;
  border-radius: 12px;
}
#search::placeholder, .qinput::placeholder { color: var(--muted); opacity: 0.85; }

.company-actions { display: flex; flex-wrap: wrap; gap: 0.5rem; margin: 1rem 0; }
.company-actions a, .prob-row .links a {
  display: inline-flex;
  align-items: center;
  min-height: 2rem;
  padding: 0.28rem 0.62rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface-solid);
  text-decoration: none;
}
.company-actions a:hover, .prob-row .links a:hover {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.prob-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.8rem;
}
.prob-row {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  grid-template-areas:
    "star title status"
    ". reports links";
  align-items: start;
  gap: 0.5rem 0.65rem;
  min-width: 0;
  padding: 1rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: var(--shadow-sm);
  backdrop-filter: var(--backdrop);
  -webkit-backdrop-filter: var(--backdrop);
}
.prob-row:hover {
  transform: translateY(-2px);
  border-color: var(--border-strong);
  box-shadow: var(--shadow-md);
}
.prob-row .star { grid-area: star; font-size: 1.05rem; }
.prob-row .title { grid-area: title; min-width: 0; line-height: 1.35; }
.prob-row .concept { display: block; margin-top: 0.28rem; font-weight: 450; line-height: 1.35; }
.prob-row .study-status { grid-area: status; }
.prob-row .reports { grid-area: reports; align-self: center; }
.prob-row .links { grid-area: links; display: flex; flex-wrap: wrap; justify-content: flex-end; gap: 0.35rem; }
.prob-row .links a { margin-left: 0; font-size: 0.78rem; }

.page-head, .page-header {
  max-width: 78ch;
  padding: 1.1rem 1.2rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: var(--shadow-sm);
  backdrop-filter: var(--backdrop);
  -webkit-backdrop-filter: var(--backdrop);
}
body > .page-head, body > .page-header { max-width: min(78ch, calc(100% - 3rem)); margin-top: 1.5rem; }
.page-head h1, .page-header h1 { letter-spacing: -0.035em; }

main.page, main.prose, main.reference, main.page-body { max-width: 860px; }
main.page > section, main.prose > section, main.reference > section,
main.page-body > section { margin-inline: auto; }
main h2 {
  padding-bottom: 0.38rem;
  border-bottom: 1px solid var(--border);
  letter-spacing: -0.025em;
}

.recall-panel, .visualization-scene, .viz, section.slide, .quiz-card {
  box-shadow: var(--shadow-sm);
  backdrop-filter: var(--backdrop);
  -webkit-backdrop-filter: var(--backdrop);
}
.recall-panel { border-radius: 16px; padding: 1.15rem 1.25rem; }
.recall-panel summary { padding: 0.15rem 0; }
.recall-panel details[open] summary { color: var(--accent); }

.visualization-scene { border-radius: 14px; }
.viz { border-radius: 14px; }
.viz-frame { border-radius: 10px; }

pre { border-color: var(--border-strong); border-radius: 12px; box-shadow: inset 0 1px 0 rgba(255,255,255,0.04); }
p code, li code { border: 1px solid color-mix(in srgb, var(--border) 72%, transparent); }

body.deck { width: min(100% - 2rem, 820px); }
.deck-head {
  padding: 1rem 1.1rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: var(--shadow-sm);
}
.deck-progress { margin: 1.1rem 0 0.35rem; }
section.slide {
  min-height: 20rem;
  border-radius: 16px;
  padding: clamp(1.1rem, 4vw, 2rem);
  box-shadow: var(--shadow-md);
}
.deck-foot, .deck-footer, .deck-nav {
  padding: 0.7rem;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--surface);
  box-shadow: var(--shadow-sm);
  backdrop-filter: var(--backdrop);
  -webkit-backdrop-filter: var(--backdrop);
}

.quiz-card { border-radius: 14px; padding: 1.1rem 1.2rem; }
.quiz-card:hover { border-color: var(--border-strong); }
.quiz-card label { padding: 0.35rem 0.25rem; border-radius: 7px; }
.quiz-card label:hover { background: var(--surface-hover); }
#score {
  top: 0.65rem;
  border-radius: 12px;
  box-shadow: var(--shadow-sm);
  backdrop-filter: var(--backdrop);
  -webkit-backdrop-filter: var(--backdrop);
}

@media (max-width: 900px) {
  .prob-list { grid-template-columns: 1fr; }
  .site + main { max-width: 760px; }
}

@media (max-width: 720px) {
  body { background-attachment: scroll; }
  .theme-toggle { top: auto; right: 0.75rem; bottom: 0.75rem; }
  header.site { padding: 1.3rem 1rem 1.1rem; }
  header.site .sub { padding-right: 0; }
  .site + main { padding-top: 1rem; }
  .tabs { width: 100%; display: grid; grid-template-columns: repeat(3, 1fr); }
  .tabs button { padding-inline: 0.35rem; }

  .prob-row {
    grid-template-columns: auto minmax(0, 1fr) auto;
    grid-template-areas:
      "star title status"
      ". reports reports"
      ". links links";
    padding: 0.9rem;
  }
  .prob-row .title { flex-basis: auto; }
  .prob-row .reports { margin-left: 0; }
  .prob-row .links { margin-left: 0; justify-content: flex-start; }

  body > .page-head, body > .page-header { max-width: calc(100% - 2rem); margin-top: 1rem; }
  .page-head, .page-header { padding: 0.9rem 1rem; }
  .recall-panel { padding: 1rem; }
  .recall-actions { align-items: stretch; }
  .recall-actions > strong { flex-basis: 100%; }

  body.deck { width: min(100% - 1rem, 820px); margin-block: 0.5rem; }
  .deck-head { padding: 0.85rem 1rem; }
  section.slide { border-radius: 13px; }
  .deck-foot, .deck-footer, .deck-nav {
    border-radius: 12px 12px 0 0;
    backdrop-filter: var(--backdrop);
    -webkit-backdrop-filter: var(--backdrop);
  }
}

@media print {
  .theme-toggle, .deck-steps, .deck-foot, .deck-footer, .deck-nav,
  .code-toolbar, .recall-actions { display: none !important; }
  body { background: #fff; color: #111; }
  .prob-row, .quiz-card, section.slide, .recall-panel { box-shadow: none; }
}