/* ============================================================
   Oncology Clinical Programming Tutor — Shared Design System
   Apple / OpenAI–inspired: neutral palette, system sans type,
   generous whitespace, soft rounded surfaces, restrained accent.
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Inter:ital,wght@0,400;0,500;0,600;0,700;0,800;1,400&display=swap');

:root {
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, 'SF Mono', 'SFMono-Regular', Menlo, Consolas, 'Liberation Mono', monospace;

  --line: #30d158;
  --gold: #0a84ff;
  --gold-light: #409cff;
  --white: #f5f5f7;
  --muted: #98989d;
  --bg: #000000;
  --card-bg: #1c1c1e;
  --card-border: rgba(255,255,255,0.09);
  --danger: #ff453a;
  --blue: #0a84ff;
  --purple: #bf5af2;
  --orange: #ff9f0a;
  --teal: #63e6e2;
  --text-secondary: #c7c7cc;
  --code-bg: #1c1c1e;
  --code-text: #f5f5f7;
  --stripe-color: transparent;

  --divider: rgba(255,255,255,0.09);
  --panel-bg: rgba(255,255,255,0.045);
  --success-bg: rgba(48,209,88,0.14);
  --danger-bg: rgba(255,69,58,0.14);
  --accent-bg: rgba(10,132,255,0.16);
  --track-bg: rgba(255,255,255,0.08);

  --radius-sm: 10px;
  --radius-md: 16px;
  --radius-lg: 22px;

  --shadow-sm: 0 1px 2px rgba(0,0,0,0.4);
  --shadow-md: 0 10px 30px rgba(0,0,0,0.45);
}

/* ============ Light theme ============ */
:root[data-theme="light"] {
  --line: #248a3d;
  --gold: #0071e3;
  --gold-light: #0077ed;
  --white: #1d1d1f;
  --muted: #6e6e73;
  --bg: #ffffff;
  --card-bg: #f5f5f7;
  --card-border: rgba(0,0,0,0.08);
  --danger: #d70015;
  --blue: #0071e3;
  --purple: #8944ab;
  --orange: #c2410c;
  --teal: #0f8a80;
  --text-secondary: #424245;
  --stripe-color: transparent;

  --divider: rgba(0,0,0,0.08);
  --panel-bg: rgba(0,0,0,0.035);
  --success-bg: rgba(36,138,61,0.10);
  --danger-bg: rgba(215,0,21,0.08);
  --accent-bg: rgba(0,113,227,0.08);
  --track-bg: rgba(0,0,0,0.06);

  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 12px 32px rgba(0,0,0,0.10);
  /* --code-bg / --code-text stay dark in both themes so syntax highlighting keeps working contrast */
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--white);
  font-family: var(--font-sans);
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
  overflow-x: hidden;
  transition: background-color 0.25s ease, color 0.25s ease;
}

/* Background texture (kept as a hook; intentionally flat/transparent for the minimal look) */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background: var(--stripe-color);
  pointer-events: none;
  z-index: 0;
}

/* ============ Theme toggle button ============ */
#onco-theme-toggle {
  position: fixed;
  top: 1.25rem;
  right: 1.25rem;
  z-index: 100;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 1px solid var(--card-border);
  background: var(--card-bg);
  color: var(--white);
  font-size: 1.05rem;
  line-height: 1;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-sm);
  transition: all 0.2s ease;
}

#onco-theme-toggle:hover { border-color: var(--gold); transform: scale(1.06); }

@media (max-width: 600px) {
  #onco-theme-toggle { width: 36px; height: 36px; font-size: 0.95rem; top: 0.85rem; right: 0.85rem; }
}

.container {
  max-width: 760px;
  margin: 0 auto;
  padding: 2rem 1.5rem 6rem;
  position: relative;
  z-index: 1;
}

.container.wide { max-width: 1100px; }

a { color: inherit; }

/* ============ Top Bar (lessons) ============ */
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 0.75rem;
  padding: 1rem 0;
  border-bottom: 1px solid var(--divider);
  margin-bottom: 1rem;
  position: relative;
  z-index: 2;
}

.topbar-left, .topbar-right {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.back-link {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.8rem;
  letter-spacing: -0.005em;
  color: var(--muted);
  text-decoration: none;
  border: 1px solid var(--card-border);
  padding: 0.5rem 0.9rem;
  border-radius: var(--radius-sm);
  transition: all 0.2s;
  white-space: nowrap;
}

.back-link:hover { border-color: var(--gold); color: var(--gold); }

.module-tag {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.72rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--line);
}

.lesson-counter {
  font-family: var(--font-sans);
  font-weight: 500;
  font-size: 0.8rem;
  color: var(--muted);
  white-space: nowrap;
}

/* ============ Header ============ */
.header {
  text-align: center;
  padding: 3rem 0 2rem;
  position: relative;
}

.lesson-tag {
  display: inline-block;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--gold);
  border: 1px solid var(--card-border);
  padding: 0.35rem 0.85rem;
  border-radius: 999px;
  margin-bottom: 1.25rem;
  background: var(--accent-bg);
}

h1 {
  font-family: var(--font-sans);
  font-weight: 800;
  font-size: clamp(2.1rem, 6vw, 3.75rem);
  line-height: 1.08;
  letter-spacing: -0.02em;
  color: var(--white);
  margin-bottom: 0.5rem;
}

h1 span { color: var(--gold); }

.subtitle {
  color: var(--muted);
  font-size: 1.0625rem;
  font-weight: 400;
  line-height: 1.55;
  margin-top: 0.85rem;
  letter-spacing: 0;
  max-width: 34rem;
  margin-left: auto;
  margin-right: auto;
}

/* ============ Progress bar (dots) ============ */
.progress-bar {
  display: flex;
  gap: 7px;
  justify-content: center;
  margin: 2rem 0;
  flex-wrap: wrap;
}

.progress-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--track-bg);
  transition: all 0.3s ease;
  cursor: pointer;
}

.progress-dot.active { background: var(--gold); transform: scale(1.4); }
.progress-dot.done { background: var(--line); }

/* ============ Sections ============ */
.section { display: none; animation: fadeSlide 0.5s ease forwards; }
.section.active { display: block; }

@keyframes fadeSlide {
  from { opacity: 0; transform: translateY(16px); }
  to { opacity: 1; transform: translateY(0); }
}

.section-title {
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 1.6rem;
  letter-spacing: -0.01em;
  color: var(--white);
  margin-bottom: 0.3rem;
}

.section-num {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.75rem;
  color: var(--gold);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin-bottom: 0.5rem;
}

/* ============ Cards ============ */
.card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-md);
  padding: 1.5rem 1.6rem;
  margin: 1rem 0;
}

.card p { color: var(--text-secondary); line-height: 1.7; font-size: 1rem; }
.card p + p { margin-top: 0.75rem; }

/* ============ Sport / generic 3-col grid ============ */
.sport-grid, .three-col-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.75rem;
  margin: 1.25rem 0;
}

.sport-card, .flip-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-md);
  padding: 1.4rem 1.1rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.25s ease;
  position: relative;
  overflow: hidden;
}

.sport-card:hover, .flip-card:hover { transform: translateY(-2px); border-color: var(--muted); box-shadow: var(--shadow-sm); }

.sport-card.revealed, .flip-card.revealed {
  border-color: var(--gold);
  background: var(--accent-bg);
}

.sport-card.oncology-card.revealed {
  border-color: var(--line);
  background: var(--success-bg);
}

.sport-emoji, .flip-emoji { font-size: 2.25rem; display: block; margin-bottom: 0.6rem; }
.sport-name, .flip-name { font-family: var(--font-sans); font-weight: 700; font-size: 1.05rem; letter-spacing: -0.005em; }
.sport-ta { font-size: 0.8rem; color: var(--muted); margin-top: 0.25rem; }
.sport-desc, .flip-desc {
  font-size: 0.85rem;
  color: var(--muted);
  margin-top: 0.7rem;
  line-height: 1.55;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s ease;
}
.sport-card.revealed .sport-desc, .flip-card.revealed .flip-desc { max-height: 200px; }

.click-hint {
  font-size: 0.8rem;
  color: var(--muted);
  text-align: center;
  margin-top: 0.5rem;
  font-style: normal;
  opacity: 0.85;
}

/* ============ Question cards (3-col numbered) ============ */
.questions-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.75rem;
  margin: 1.25rem 0;
}

.q-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-md);
  padding: 1.4rem 1.1rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.3s ease;
}

.q-card:hover { transform: translateY(-2px); box-shadow: var(--shadow-sm); }

.q-card[data-color="blue"] { --accent: var(--blue); }
.q-card[data-color="purple"] { --accent: var(--purple); }
.q-card[data-color="teal"] { --accent: var(--teal); }
.q-card[data-color="gold"] { --accent: var(--gold); }
.q-card[data-color="green"] { --accent: var(--line); }
.q-card[data-color="orange"] { --accent: var(--orange); }

.q-card.revealed { border-color: var(--accent); background: var(--panel-bg); }

.q-num {
  width: 36px; height: 36px;
  border-radius: 50%;
  border: 2px solid var(--accent, var(--card-border));
  display: flex; align-items: center; justify-content: center;
  margin: 0 auto 0.75rem;
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--accent, var(--muted));
  transition: all 0.3s;
}

.q-card.revealed .q-num { background: var(--accent); color: #fff; }

.q-label {
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 1rem;
  letter-spacing: -0.005em;
  color: var(--white);
  margin-bottom: 0.35rem;
}

.q-answer {
  font-size: 0.82rem;
  color: var(--muted);
  line-height: 1.55;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s ease;
}

.q-card.revealed .q-answer { max-height: 200px; color: var(--muted); }

/* ============ Interactive table (endpoint-style) ============ */
.endpoint-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.25rem 0;
  font-size: 0.9rem;
}

.endpoint-table th {
  text-align: left;
  padding: 0.65rem 0.75rem;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.7rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
  border-bottom: 1px solid var(--divider);
}

.endpoint-row { cursor: pointer; transition: all 0.2s; }

.endpoint-row td {
  padding: 0.8rem 0.75rem;
  border-bottom: 1px solid var(--divider);
  vertical-align: top;
  color: var(--text-secondary);
}

.endpoint-row:hover td { background: var(--panel-bg); }
.endpoint-row.selected td { background: var(--accent-bg); }

.endpoint-row td:first-child {
  font-family: var(--font-sans);
  font-size: 0.9rem;
  color: var(--gold);
  font-weight: 700;
  white-space: nowrap;
}

.endpoint-detail { display: none; background: var(--panel-bg); padding: 1rem 0.75rem; border-bottom: 1px solid var(--divider); }
.endpoint-detail.visible { display: table-row; }
.endpoint-detail td { padding: 1rem 0.75rem; color: var(--muted); font-size: 0.88rem; line-height: 1.7; }

.complexity-bar { display: flex; align-items: center; gap: 0.5rem; margin-top: 0.5rem; }
.complexity-label { font-family: var(--font-sans); font-weight: 600; font-size: 0.68rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.06em; width: 84px; }
.bar-track { flex: 1; height: 6px; background: var(--track-bg); border-radius: 3px; overflow: hidden; }
.bar-fill { height: 100%; border-radius: 3px; background: var(--gold); transition: width 0.6s ease; }

/* Plain data table */
.data-table { width: 100%; border-collapse: collapse; margin: 1.25rem 0; font-size: 0.88rem; overflow-x: auto; display: block; }
.data-table thead, .data-table tbody { display: table; width: 100%; table-layout: fixed; }
.data-table th { text-align: left; padding: 0.65rem 0.75rem; font-family: var(--font-sans); font-weight: 600; font-size: 0.68rem; letter-spacing: 0.05em; text-transform: uppercase; color: var(--muted); border-bottom: 1px solid var(--divider); background: var(--panel-bg); }
.data-table td { padding: 0.7rem 0.75rem; border-bottom: 1px solid var(--divider); color: var(--text-secondary); font-family: var(--font-mono); font-size: 0.82rem; }
.data-table tr.highlight-row td { background: var(--accent-bg); color: var(--gold); }
.data-table tr.green-row td { background: var(--success-bg); }

/* ============ Chain of derivations ============ */
.chain { display: flex; align-items: center; gap: 0; margin: 1.25rem 0; overflow-x: auto; padding: 0.5rem 0; }

.chain-step {
  flex-shrink: 0;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-sm);
  padding: 0.85rem 1.1rem;
  font-size: 0.82rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.25s;
  min-width: 112px;
}

.chain-step:hover, .chain-step.lit { border-color: var(--gold); background: var(--accent-bg); }
.chain-step.error { border-color: var(--danger); background: var(--danger-bg); animation: shake 0.4s ease; }
.chain-step.good { border-color: var(--line); background: var(--success-bg); }

@keyframes shake {
  0%,100% { transform: translateX(0); }
  25% { transform: translateX(-4px); }
  75% { transform: translateX(4px); }
}

.chain-arrow { color: var(--muted); font-size: 1.2rem; padding: 0 0.25rem; flex-shrink: 0; }
.chain-icon { font-size: 1.35rem; display: block; margin-bottom: 0.3rem; }
.chain-label { font-size: 0.72rem; color: var(--muted); }
.chain-name { font-weight: 600; font-size: 0.82rem; color: var(--white); }

.chain-note {
  font-size: 0.85rem;
  color: var(--muted);
  text-align: center;
  margin-top: 0.5rem;
  font-style: normal;
  min-height: 1.2em;
  transition: color 0.3s;
}

/* ============ Variable explorer cards (reused across lessons) ============ */
.var-card { background: var(--card-bg); border: 1px solid var(--card-border); border-radius: var(--radius-md); margin: 0.6rem 0; overflow: hidden; cursor: pointer; transition: border-color 0.2s; }
.var-card:hover { border-color: var(--muted); }
.var-card.open { border-color: var(--gold); }
.var-head { padding: 0.95rem 1.15rem; display: flex; justify-content: space-between; align-items: center; gap: 1rem; }
.var-name { font-family: var(--font-mono); font-size: 0.85rem; color: var(--gold); font-weight: 500; }
.var-label { font-size: 0.82rem; color: var(--muted); margin-left: 0.6rem; }
.var-chevron { color: var(--muted); transition: transform 0.3s; flex-shrink: 0; }
.var-card.open .var-chevron { transform: rotate(180deg); color: var(--gold); }
.var-body { max-height: 0; overflow: hidden; transition: max-height 0.4s ease; padding: 0 1.15rem; }
.var-card.open .var-body { max-height: 240px; padding: 0 1.15rem 1.1rem; }
.var-body p { color: var(--muted); font-size: 0.87rem; line-height: 1.6; }
.var-body .example { font-family: var(--font-mono); color: var(--line); margin-top: 0.4rem; font-size: 0.8rem; }

/* ============ Pitfall / expandable accordion cards ============ */
.pitfall-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-md);
  margin: 0.75rem 0;
  overflow: hidden;
  cursor: pointer;
  transition: border-color 0.2s;
}

.pitfall-card:hover { border-color: var(--muted); }
.pitfall-card.open { border-color: var(--gold); }

.pitfall-head {
  padding: 1.05rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.92rem;
  color: var(--white);
}

.pitfall-num {
  font-family: var(--font-sans);
  font-weight: 700;
  color: var(--gold);
  margin-right: 0.6rem;
}

.pitfall-chevron { color: var(--muted); transition: transform 0.3s; flex-shrink: 0; }
.pitfall-card.open .pitfall-chevron { transform: rotate(180deg); color: var(--gold); }

.pitfall-body {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s ease;
  padding: 0 1.25rem;
}

.pitfall-card.open .pitfall-body { max-height: 400px; padding: 0 1.25rem 1.25rem; }

.pitfall-body p { color: var(--muted); font-size: 0.87rem; line-height: 1.65; }
.pitfall-body .solution { color: var(--line); margin-top: 0.5rem; }

/* ============ Classifier / drag-drop style click-to-classify ============ */
.classifier-zone {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.75rem;
  margin: 1rem 0;
}

.classify-bucket {
  background: var(--panel-bg);
  border: 1px dashed var(--card-border);
  border-radius: var(--radius-md);
  padding: 0.75rem;
  min-height: 140px;
}

.classify-bucket-label {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.72rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.5rem;
  text-align: center;
}

.lesion-pool { display: flex; flex-wrap: wrap; gap: 0.5rem; margin: 1rem 0; justify-content: center; }

.lesion-chip {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 999px;
  padding: 0.55rem 1.05rem;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  cursor: pointer;
  transition: all 0.2s;
}

.lesion-chip:hover { border-color: var(--gold); transform: translateY(-2px); }
.lesion-chip.placed { opacity: 0.35; cursor: default; }
.lesion-chip.correct-place { border-color: var(--line); background: var(--success-bg); }
.lesion-chip.wrong-place { border-color: var(--danger); background: var(--danger-bg); }

.classify-bucket .lesion-chip { margin: 0.25rem; display: inline-block; }

/* ============ Code tabs ============ */
.code-block {
  margin: 1.25rem 0;
  border: 1px solid var(--card-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  background: var(--code-bg);
  box-shadow: var(--shadow-sm);
}

.code-tabs {
  display: flex;
  background: rgba(255,255,255,0.04);
  border-bottom: 1px solid rgba(255,255,255,0.08);
}

.code-tab {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.78rem;
  letter-spacing: 0.02em;
  color: #98989d;
  padding: 0.65rem 1.25rem;
  cursor: pointer;
  border: none;
  background: transparent;
  transition: all 0.2s;
  border-bottom: 2px solid transparent;
}

.code-tab.active { color: var(--gold-light); border-bottom-color: var(--gold-light); background: rgba(10,132,255,0.08); }

.code-copy-btn {
  margin-left: auto;
  font-family: var(--font-sans);
  font-weight: 500;
  font-size: 0.75rem;
  color: #98989d;
  background: transparent;
  border: none;
  cursor: pointer;
  padding: 0.65rem 1.1rem;
  transition: color 0.2s;
}

.code-copy-btn:hover { color: #f5f5f7; }

.code-panel { display: none; }
.code-panel.active { display: block; }

.code-panel pre {
  margin: 0;
  padding: 1.2rem 1.3rem;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  line-height: 1.65;
  color: var(--code-text);
}

.code-panel code { font-family: var(--font-mono); }

/* syntax accents (no highlight.js dependency) */
.tok-kw { color: #ff9f0a; }
.tok-str { color: #32d74b; }
.tok-cm  { color: #86868b; font-style: italic; }
.tok-fn  { color: #0a84ff; }
.tok-num { color: #bf5af2; }

/* ============ Quiz ============ */
.quiz-q { font-size: 1.05rem; font-weight: 600; color: var(--white); margin-bottom: 1rem; line-height: 1.55; letter-spacing: -0.005em; }
.quiz-options { display: flex; flex-direction: column; gap: 0.55rem; margin-bottom: 1rem; }

.quiz-opt {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-sm);
  padding: 0.9rem 1.15rem;
  cursor: pointer;
  font-size: 0.95rem;
  color: var(--text-secondary);
  text-align: left;
  transition: all 0.2s;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  width: 100%;
  min-height: 48px;
  font-family: var(--font-sans);
}

.quiz-opt:hover:not(:disabled) { border-color: var(--muted); background: var(--panel-bg); }
.quiz-opt.correct { border-color: var(--line); background: var(--success-bg); color: var(--white); }
.quiz-opt.wrong { border-color: var(--danger); background: var(--danger-bg); }
.quiz-opt:disabled { cursor: default; }

.opt-letter {
  width: 26px; height: 26px;
  border-radius: 50%;
  border: 1px solid var(--card-border);
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 0.72rem;
  flex-shrink: 0;
  transition: all 0.2s;
}

.quiz-opt.correct .opt-letter { background: var(--line); border-color: var(--line); color: #fff; }
.quiz-opt.wrong .opt-letter { background: var(--danger); border-color: var(--danger); color: #fff; }

.quiz-feedback {
  background: var(--panel-bg);
  border-left: 3px solid var(--line);
  padding: 1rem 1.25rem;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  font-size: 0.9rem;
  color: var(--muted);
  line-height: 1.65;
  display: none;
  margin-top: 0.75rem;
}

.quiz-feedback.visible { display: block; }
.quiz-feedback.wrong-fb { border-left-color: var(--gold); }

/* ============ Bottom nav ============ */
.nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--divider);
  gap: 0.75rem;
  flex-wrap: wrap;
}

.nav-btn {
  background: transparent;
  border: 1px solid var(--card-border);
  color: var(--white);
  padding: 0.75rem 1.4rem;
  border-radius: 999px;
  cursor: pointer;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.85rem;
  letter-spacing: 0;
  transition: all 0.2s;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  max-width: 45%;
  min-height: 44px;
}

.nav-btn:hover { border-color: var(--gold); color: var(--gold); }
.nav-btn:disabled, .nav-btn.disabled { opacity: 0.3; cursor: default; pointer-events: none; }
.nav-btn.primary { background: var(--gold); color: #fff; border-color: var(--gold); font-weight: 600; }
.nav-btn.primary:hover { background: var(--gold-light); color: #fff; border-color: var(--gold-light); }

.nav-counter { font-family: var(--font-sans); font-weight: 500; font-size: 0.82rem; color: var(--muted); }

/* bottom prev/next lesson bar (site-wide, separate from section-nav) */
.lesson-nav {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--divider);
  flex-wrap: wrap;
}

.lesson-nav-btn {
  flex: 1;
  min-width: 200px;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-md);
  padding: 1.1rem 1.3rem;
  text-decoration: none;
  color: var(--white);
  transition: all 0.2s;
  display: block;
}

.lesson-nav-btn:hover { border-color: var(--gold); transform: translateY(-2px); box-shadow: var(--shadow-sm); }
.lesson-nav-btn.next { text-align: right; }
.lesson-nav-btn .ln-label { font-family: var(--font-sans); font-weight: 600; font-size: 0.7rem; letter-spacing: 0.06em; text-transform: uppercase; color: var(--muted); }
.lesson-nav-btn .ln-title { font-family: var(--font-sans); font-weight: 700; font-size: 1.05rem; letter-spacing: -0.005em; color: var(--gold); margin-top: 0.25rem; }
.lesson-nav-btn.disabled { opacity: 0.3; pointer-events: none; }
.lesson-nav-btn.celebrate .ln-title { color: var(--line); }

/* ============ Highlights / callouts ============ */
.hl { color: var(--gold); font-weight: 600; }
.hl-green { color: var(--line); font-weight: 600; }

.callout {
  border: 1px solid var(--card-border);
  background: var(--accent-bg);
  border-radius: var(--radius-md);
  padding: 1.1rem 1.3rem;
  margin: 1rem 0;
  font-size: 0.92rem;
  color: var(--text-secondary);
  line-height: 1.65;
}

.callout.green { background: var(--success-bg); }
.callout.danger { background: var(--danger-bg); }
.callout-icon { font-size: 1.1rem; margin-right: 0.4rem; }

/* ============ Completion panel ============ */
.completion { text-align: center; padding: 2rem 1rem; }

.completion-badge {
  width: 76px; height: 76px;
  border-radius: 50%;
  background: var(--success-bg);
  border: 2px solid var(--line);
  display: flex; align-items: center; justify-content: center;
  font-size: 2.25rem;
  margin: 0 auto 1.5rem;
  animation: pulse 2s ease infinite;
}

@keyframes pulse {
  0%,100% { box-shadow: 0 0 0 0 rgba(48,209,88,0.3); }
  50% { box-shadow: 0 0 0 12px rgba(48,209,88,0); }
}

.completion h2 {
  font-family: var(--font-sans);
  font-weight: 800;
  font-size: 2rem;
  letter-spacing: -0.015em;
  color: var(--line);
  margin-bottom: 0.5rem;
}

.key-takeaways { text-align: left; margin-top: 1.5rem; }

.takeaway {
  display: flex;
  gap: 0.75rem;
  align-items: flex-start;
  padding: 0.8rem 0;
  border-bottom: 1px solid var(--divider);
  font-size: 0.9rem;
  color: var(--muted);
  line-height: 1.55;
}

.takeaway-icon { flex-shrink: 0; font-size: 1rem; margin-top: 0.1rem; }

/* ============ Segmented tabs (generic multi-way toggle) ============ */
.seg-tabs { display: flex; gap: 0.5rem; margin: 1rem 0; flex-wrap: wrap; }
.seg-tab {
  flex: 1;
  min-width: 100px;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  color: var(--white);
  padding: 0.75rem 1rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.82rem;
  letter-spacing: 0;
  transition: all 0.2s;
  min-height: 44px;
}
.seg-tab.active { border-color: var(--gold); background: var(--accent-bg); color: var(--gold); }
.seg-panel { display: none; }
.seg-panel.active { display: block; animation: fadeSlide 0.35s ease; }

/* ============ Index page specific ============ */
.dashboard-header { text-align: center; padding: 3.5rem 0 2rem; }

.overall-progress {
  max-width: 480px;
  margin: 1.75rem auto 0;
}

.overall-progress-label {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.8rem;
  color: var(--muted);
  letter-spacing: 0;
  margin-bottom: 0.5rem;
  display: flex;
  justify-content: space-between;
}

.overall-progress-track {
  height: 8px;
  background: var(--track-bg);
  border-radius: 4px;
  overflow: hidden;
}

.overall-progress-fill {
  height: 100%;
  background: var(--gold);
  border-radius: 4px;
  transition: width 0.6s ease;
}

.module-block { margin: 2.75rem 0; }

.module-header {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  margin-bottom: 1.1rem;
  flex-wrap: wrap;
}

.module-num {
  font-family: var(--font-sans);
  font-weight: 800;
  font-size: 1.4rem;
  color: var(--gold);
  line-height: 1;
}

.module-title {
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 1.3rem;
  letter-spacing: -0.01em;
  color: var(--white);
}

.module-sub { font-size: 0.85rem; color: var(--muted); font-family: var(--font-sans); font-weight: 500; }

.lesson-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1rem;
}

.lesson-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-md);
  padding: 1.4rem;
  text-decoration: none;
  color: var(--white);
  transition: all 0.25s;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
  position: relative;
}

.lesson-card:hover { transform: translateY(-3px); border-color: var(--gold); box-shadow: var(--shadow-md); }

.lesson-card-top { display: flex; justify-content: space-between; align-items: flex-start; gap: 0.5rem; }

.lesson-num-badge {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.72rem;
  color: var(--muted);
  letter-spacing: 0.05em;
}

.status-badge {
  font-size: 0.72rem;
  font-family: var(--font-sans);
  font-weight: 600;
  padding: 0.2rem 0.6rem;
  border-radius: 999px;
  white-space: nowrap;
}

.status-badge.complete { background: var(--success-bg); color: var(--line); border: 1px solid var(--line); }
.status-badge.in-progress { background: var(--accent-bg); color: var(--blue); border: 1px solid var(--blue); }
.status-badge.not-started { background: var(--panel-bg); color: var(--muted); border: 1px solid var(--card-border); }

.lesson-card-title {
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: -0.005em;
  line-height: 1.3;
}

.lesson-card-desc { font-size: 0.85rem; color: var(--muted); line-height: 1.5; }

.dashboard-footer {
  text-align: center;
  margin-top: 3.5rem;
  padding-top: 2rem;
  border-top: 1px solid var(--divider);
  font-size: 0.85rem;
  color: var(--muted);
  font-family: var(--font-sans);
  font-weight: 500;
  letter-spacing: 0;
}

/* ============ Responsive ============ */
@media (max-width: 768px) {
  .sport-grid, .three-col-grid, .questions-grid, .classifier-zone { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 600px) {
  .sport-grid, .three-col-grid, .questions-grid, .classifier-zone { grid-template-columns: 1fr; }
  .chain { flex-direction: column; }
  .chain-arrow { transform: rotate(90deg); }
  .topbar { flex-direction: column; align-items: stretch; text-align: center; }
  .lesson-nav-btn.next { text-align: left; }
  .nav-btn { max-width: 100%; }
  .container { padding: 1.5rem 1.25rem 5rem; }
  .card { padding: 1.25rem 1.15rem; }
  .quiz-q { font-size: 1rem; }
  .subtitle { font-size: 1rem; }
}