/* COS 102 Quiz — Human-centered, minimal design
   Created with love by gentlesoul.dev */

:root {
  --bg: #faf9f7;
  --surface: #ffffff;
  --surface-2: #f3f1ee;
  --ink: #1a1a1a;
  --ink-2: #4a4a4a;
  --ink-3: #8a8a8a;
  --line: #e8e5e0;
  --accent: #2f6fed;
  --accent-soft: #e8f0fe;
  --good: #1a7f4b;
  --good-soft: #e6f5ed;
  --bad: #c43c3c;
  --bad-soft: #fdecec;
  --warn: #b45309;
  --radius: 14px;
  --radius-sm: 10px;
  --font: 'DM Sans', system-ui, -apple-system, sans-serif;
  --mono: 'JetBrains Mono', ui-monospace, monospace;
  --shadow: 0 1px 2px rgba(0,0,0,.04), 0 4px 12px rgba(0,0,0,.04);
  --topbar-h: 56px;
  --safe-bottom: env(safe-area-inset-bottom, 0px);
}

[data-theme="dark"] {
  --bg: #121212;
  --surface: #1c1c1c;
  --surface-2: #262626;
  --ink: #f2f2f2;
  --ink-2: #b0b0b0;
  --ink-3: #6e6e6e;
  --line: #2e2e2e;
  --accent: #5b8def;
  --accent-soft: #1a2744;
  --good: #3dba74;
  --good-soft: #143528;
  --bad: #e06c6c;
  --bad-soft: #3a1c1c;
  --warn: #e0a04a;
  --shadow: 0 1px 2px rgba(0,0,0,.2), 0 4px 12px rgba(0,0,0,.25);
}

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

html { height: 100%; -webkit-tap-highlight-color: transparent; }

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--ink);
  line-height: 1.5;
  min-height: 100%;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

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

.hidden { display: none !important; }

/* ========== OVERLAYS ========== */
.overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,.45);
  display: grid;
  place-items: center;
  z-index: 200;
  padding: 20px;
  backdrop-filter: blur(6px);
}

.onboard-card, .modal {
  background: var(--surface);
  border-radius: 20px;
  padding: 32px 28px;
  width: 100%;
  max-width: 380px;
  box-shadow: var(--shadow);
  text-align: center;
}

.onboard-icon { font-size: 40px; margin-bottom: 12px; }
.onboard-card h1 { font-size: 1.45rem; font-weight: 700; margin-bottom: 8px; letter-spacing: -0.02em; }
.onboard-card p { color: var(--ink-2); font-size: 0.95rem; margin-bottom: 20px; }
.onboard-card input {
  width: 100%;
  padding: 14px 16px;
  border: 1.5px solid var(--line);
  border-radius: 12px;
  background: var(--bg);
  margin-bottom: 8px;
  font-size: 1rem;
}
.onboard-card input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}
.hint { font-size: 0.8rem; color: var(--bad); min-height: 1.2em; margin-bottom: 12px !important; }
.credit-mini { margin-top: 20px; font-size: 0.75rem; color: var(--ink-3); }

.modal h3 { font-size: 1.15rem; margin-bottom: 6px; }
.modal p { color: var(--ink-2); font-size: 0.9rem; margin-bottom: 20px; }
.modal-actions { display: flex; gap: 10px; justify-content: center; }

/* ========== APP SHELL ========== */
.app {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
}

.topbar {
  height: var(--topbar-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 12px 0 8px;
  background: var(--surface);
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 50;
}

.topbar-left, .topbar-right { display: flex; align-items: center; gap: 8px; }

.brand {
  display: flex;
  align-items: center;
  gap: 8px;
  cursor: pointer;
  user-select: none;
}
.brand-mark {
  background: var(--ink);
  color: var(--bg);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.04em;
  padding: 5px 7px;
  border-radius: 6px;
}
[data-theme="dark"] .brand-mark { background: var(--ink); color: #121212; }
.brand-text { font-weight: 600; font-size: 0.95rem; }

.user-chip {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--ink-2);
  background: var(--surface-2);
  padding: 5px 10px;
  border-radius: 100px;
  max-width: 110px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.icon-btn {
  width: 40px;
  height: 40px;
  border: none;
  background: transparent;
  border-radius: 10px;
  display: grid;
  place-items: center;
  color: var(--ink-2);
  cursor: pointer;
}
.icon-btn:hover { background: var(--surface-2); color: var(--ink); }

[data-theme="dark"] .icon-sun { display: none; }
[data-theme="light"] .icon-moon,
:root:not([data-theme="dark"]) .icon-moon { display: none; }
[data-theme="dark"] .icon-moon { display: block; }

/* Sidebar */
.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  width: 260px;
  background: var(--surface);
  border-right: 1px solid var(--line);
  z-index: 60;
  transform: translateX(-100%);
  transition: transform 0.25s ease;
  display: flex;
  flex-direction: column;
  padding-top: var(--topbar-h);
}
.sidebar.open { transform: translateX(0); }

.sidebar-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,.3);
  z-index: 55;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s;
}
.sidebar-backdrop.show { opacity: 1; pointer-events: auto; }

.side-nav { padding: 16px 12px; flex: 1; }
.nav-item {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 14px;
  border: none;
  background: transparent;
  border-radius: 10px;
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--ink-2);
  cursor: pointer;
  text-align: left;
  margin-bottom: 2px;
}
.nav-item:hover { background: var(--surface-2); color: var(--ink); }
.nav-item.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.nav-icon { font-size: 1.1rem; width: 24px; text-align: center; opacity: 0.9; }

.sidebar-footer {
  padding: 16px 20px;
  border-top: 1px solid var(--line);
  font-size: 0.75rem;
  color: var(--ink-3);
  line-height: 1.4;
}

/* Main */
.main {
  flex: 1;
  overflow-y: auto;
  padding-bottom: calc(24px + var(--safe-bottom));
}

.page { display: none; }
.page.active { display: block; animation: fade .28s ease; }

@keyframes fade {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: none; }
}

.page-inner {
  max-width: 640px;
  margin: 0 auto;
  padding: 28px 20px 40px;
}

.page-title {
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  margin-bottom: 6px;
}
.page-desc { color: var(--ink-2); margin-bottom: 28px; font-size: 0.95rem; }

/* Hero */
.hero { margin-bottom: 36px; }
.eyebrow {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent);
  letter-spacing: 0.02em;
  margin-bottom: 10px;
}
.hero h1 {
  font-size: clamp(1.8rem, 5vw, 2.4rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: 12px;
}
.lede {
  color: var(--ink-2);
  font-size: 1.05rem;
  max-width: 420px;
  margin-bottom: 24px;
}

/* Stats */
.stats-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
  margin-bottom: 36px;
}
.stat-card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 12px;
  text-align: center;
}
.stat-card .num {
  font-size: 1.4rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  display: block;
}
.stat-card .lbl {
  font-size: 0.72rem;
  color: var(--ink-3);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  font-weight: 500;
}

.section { margin-top: 8px; }
.section-title {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--ink-3);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 12px;
}

.topic-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.chip {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 100px;
  padding: 8px 14px;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--ink-2);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 11px 18px;
  border-radius: 12px;
  border: none;
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  transition: transform .15s, opacity .15s, background .15s;
}
.btn:active { transform: scale(0.98); }
.btn:disabled { opacity: 0.4; cursor: not-allowed; }
.btn-lg { padding: 14px 24px; font-size: 1rem; border-radius: 14px; }
.btn-block { width: 100%; }
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:hover:not(:disabled) { filter: brightness(1.08); }
.btn-secondary {
  background: var(--surface);
  color: var(--ink);
  border: 1.5px solid var(--line);
}
.btn-secondary:hover:not(:disabled) { background: var(--surface-2); }
.btn-ghost { background: transparent; color: var(--ink-2); }
.btn-ghost:hover { color: var(--ink); background: var(--surface-2); }
.btn-danger { background: var(--bad); color: #fff; }
.text-btn {
  background: none;
  border: none;
  color: var(--ink-2);
  font-weight: 500;
  font-size: 0.9rem;
  cursor: pointer;
  padding: 4px 0;
}
.text-btn:hover { color: var(--ink); }

/* Practice setup */
.setup-card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
}

.field-label {
  display: block;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--ink-3);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 10px;
}

.topic-select {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 24px;
  max-height: 280px;
  overflow-y: auto;
}

.topic-option {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 14px;
  border: 1.5px solid var(--line);
  border-radius: 12px;
  cursor: pointer;
  background: var(--bg);
  transition: border-color .15s, background .15s;
  user-select: none;
}
.topic-option:hover { border-color: var(--ink-3); }
.topic-option.selected {
  border-color: var(--accent);
  background: var(--accent-soft);
}
.topic-option input { accent-color: var(--accent); width: 18px; height: 18px; }
.topic-option .t-name { font-weight: 500; font-size: 0.92rem; flex: 1; }
.topic-option .t-count { font-size: 0.78rem; color: var(--ink-3); }

.setup-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 24px;
}
@media (max-width: 480px) {
  .setup-row { grid-template-columns: 1fr; }
}

.field { margin-bottom: 4px; }

.segmented {
  display: flex;
  background: var(--surface-2);
  border-radius: 10px;
  padding: 3px;
  gap: 2px;
}
.segmented button {
  flex: 1;
  border: none;
  background: transparent;
  padding: 9px 6px;
  border-radius: 8px;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--ink-2);
  cursor: pointer;
}
.segmented button.active {
  background: var(--surface);
  color: var(--ink);
  box-shadow: 0 1px 3px rgba(0,0,0,.08);
  font-weight: 600;
}

/* Quiz */
.quiz-inner { max-width: 600px; }
.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}
.quiz-status {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--ink-2);
}
.timer {
  font-family: var(--mono);
  font-size: 0.9rem;
  background: var(--surface-2);
  padding: 4px 10px;
  border-radius: 8px;
  color: var(--ink);
}
.timer.urgent { background: var(--bad-soft); color: var(--bad); }

.progress-track {
  height: 4px;
  background: var(--line);
  border-radius: 100px;
  overflow: hidden;
  margin-bottom: 28px;
}
.progress-fill {
  height: 100%;
  background: var(--accent);
  width: 0%;
  transition: width .3s ease;
  border-radius: 100px;
}

.question-panel {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px 24px;
  box-shadow: var(--shadow);
}

.q-type {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 4px 9px;
  border-radius: 6px;
  margin-bottom: 14px;
}

.q-text {
  font-size: 1.15rem;
  font-weight: 600;
  line-height: 1.4;
  letter-spacing: -0.01em;
  margin-bottom: 24px;
}

.q-options { display: flex; flex-direction: column; gap: 8px; }

.opt {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  width: 100%;
  text-align: left;
  padding: 13px 14px;
  border: 1.5px solid var(--line);
  border-radius: 12px;
  background: var(--bg);
  cursor: pointer;
  transition: border-color .15s, background .15s;
}
.opt:hover:not(.locked) { border-color: var(--ink-3); }
.opt.selected {
  border-color: var(--accent);
  background: var(--accent-soft);
}
.opt.correct { border-color: var(--good); background: var(--good-soft); }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.opt.locked { cursor: default; }

.opt-letter {
  width: 26px;
  height: 26px;
  border-radius: 7px;
  border: 1px solid var(--line);
  background: var(--surface);
  display: grid;
  place-items: center;
  font-family: var(--mono);
  font-size: 0.75rem;
  font-weight: 600;
  flex-shrink: 0;
}
.opt.selected .opt-letter {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.opt.correct .opt-letter { background: var(--good); color: #fff; border-color: var(--good); }
.opt.wrong .opt-letter { background: var(--bad); color: #fff; border-color: var(--bad); }

.opt-text { padding-top: 2px; font-size: 0.95rem; line-height: 1.4; }

.q-input textarea {
  width: 100%;
  padding: 14px;
  border: 1.5px solid var(--line);
  border-radius: 12px;
  background: var(--bg);
  resize: vertical;
  min-height: 88px;
}
.q-input textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.q-actions {
  display: flex;
  justify-content: flex-end;
  gap: 10px;
  margin-top: 24px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
}

/* Feedback */
.feedback-panel {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px 24px;
  text-align: center;
  box-shadow: var(--shadow);
  margin-top: 16px;
}
.feedback-icon { font-size: 2rem; margin-bottom: 8px; }
.feedback-panel h3 { font-size: 1.2rem; margin-bottom: 8px; }
.feedback-panel p { color: var(--ink-2); font-size: 0.95rem; margin-bottom: 20px; line-height: 1.5; }
.feedback-panel.good h3 { color: var(--good); }
.feedback-panel.bad h3 { color: var(--bad); }

/* Results */
.results-hero { text-align: center; margin-bottom: 28px; }
.score-ring {
  width: 120px;
  height: 120px;
  margin: 0 auto 20px;
  position: relative;
}
.score-ring svg { width: 100%; height: 100%; transform: rotate(-90deg); }
.ring-bg { fill: none; stroke: var(--line); stroke-width: 8; }
.ring-fg {
  fill: none;
  stroke: var(--accent);
  stroke-width: 8;
  stroke-linecap: round;
  stroke-dasharray: 264;
  stroke-dashoffset: 264;
  transition: stroke-dashoffset 0.8s ease;
}
.score-ring span {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}
.results-hero h1 { font-size: 1.5rem; font-weight: 700; margin-bottom: 4px; }
.results-hero p { color: var(--ink-2); }

.results-meta {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 18px;
  margin-bottom: 24px;
}
.meta-row {
  display: flex;
  justify-content: space-between;
  padding: 8px 0;
  font-size: 0.9rem;
  border-bottom: 1px solid var(--line);
}
.meta-row:last-child { border-bottom: none; }
.meta-row span:first-child { color: var(--ink-2); }
.meta-row span:last-child { font-weight: 600; }

.results-actions { display: flex; flex-direction: column; gap: 8px; }

/* Review */
.review-list { display: flex; flex-direction: column; gap: 12px; margin-top: 16px; }
.review-item {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 16px;
  border-left: 3px solid var(--line);
}
.review-item.ok { border-left-color: var(--good); }
.review-item.no { border-left-color: var(--bad); }
.review-item .rq { font-weight: 600; font-size: 0.92rem; margin-bottom: 8px; }
.review-item .rm { font-size: 0.8rem; color: var(--ink-3); margin-bottom: 6px; }
.review-item .ra { font-size: 0.88rem; color: var(--ink-2); }

/* Analytics */
.analytics-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-bottom: 32px;
}
.a-card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 16px;
}
.a-card .a-num { font-size: 1.5rem; font-weight: 700; letter-spacing: -0.02em; }
.a-card .a-lbl { font-size: 0.78rem; color: var(--ink-3); margin-top: 2px; }

.session-list { display: flex; flex-direction: column; gap: 8px; }
.session-item {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.9rem;
}
.session-item .s-left { color: var(--ink-2); }
.session-item .s-score { font-weight: 600; }

/* Leaderboard */
.lb-list { display: flex; flex-direction: column; gap: 6px; }
.lb-row {
  display: flex;
  align-items: center;
  gap: 14px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
}
.lb-rank {
  width: 28px;
  height: 28px;
  border-radius: 8px;
  background: var(--surface-2);
  display: grid;
  place-items: center;
  font-weight: 700;
  font-size: 0.85rem;
  flex-shrink: 0;
}
.lb-row.top .lb-rank { background: var(--accent); color: #fff; }
.lb-name { flex: 1; font-weight: 500; }
.lb-score { font-weight: 600; font-variant-numeric: tabular-nums; }
.lb-meta { font-size: 0.75rem; color: var(--ink-3); }

.empty-state {
  text-align: center;
  padding: 40px 20px;
  color: var(--ink-3);
  font-size: 0.95rem;
}

/* Desktop */
@media (min-width: 860px) {
  .sidebar {
    transform: none;
    position: fixed;
  }
  .sidebar-backdrop { display: none !important; }
  .topbar { padding-left: 272px; }
  .main { margin-left: 260px; }
  #menuBtn { display: none; }
  .page-inner { padding-top: 36px; }
  .stats-row { grid-template-columns: repeat(3, 1fr); max-width: 480px; }
}

/* Number inputs for practice setup */
.num-input {
  width: 100%;
  padding: 12px 14px;
  border: 1.5px solid var(--line);
  border-radius: 12px;
  background: var(--bg);
  font-size: 1rem;
  font-weight: 600;
}
.num-input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}
.field-hint {
  font-size: 0.75rem;
  color: var(--ink-3);
  margin-top: 6px;
}
.setup-note {
  font-size: 0.88rem;
  color: var(--ink-2);
  margin-bottom: 16px;
  line-height: 1.45;
  padding: 12px 14px;
  background: var(--surface-2);
  border-radius: 10px;
}

/* Exam-mode submit bar */
.submit-bar {
  margin-top: 24px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
}
.answered-count {
  font-size: 0.85rem;
  color: var(--ink-3);
  text-align: center;
  margin-bottom: 10px;
}
.q-actions {
  display: flex;
  justify-content: space-between;
  gap: 10px;
  margin-top: 24px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
}

.sidebar-footer a, .credit-mini a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
}
.sidebar-footer a:hover, .credit-mini a:hover {
  text-decoration: underline;
}

.fb-status {
  font-size: 0.75rem;
  color: var(--ink-3);
  text-align: center;
  margin-top: 8px;
}
.fb-status.on { color: var(--good); }
.fb-status.off { color: var(--warn); }


/* ========== PRACTICE PAGE (redesign) ========== */
.practice-inner { max-width: 720px; }

.practice-hero { margin-bottom: 28px; }
.practice-badge {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 5px 10px;
  border-radius: 100px;
  margin-bottom: 12px;
}
.practice-hero .page-title { margin-bottom: 8px; }
.practice-hero .page-desc { margin-bottom: 0; max-width: 520px; }

.practice-block {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 18px;
  padding: 20px;
  margin-bottom: 16px;
  box-shadow: var(--shadow);
}

.block-head {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}
.step-num {
  width: 28px;
  height: 28px;
  border-radius: 9px;
  background: var(--ink);
  color: var(--bg);
  font-size: 0.85rem;
  font-weight: 700;
  display: grid;
  place-items: center;
  flex-shrink: 0;
}
[data-theme="dark"] .step-num {
  background: var(--accent);
  color: #fff;
}
.block-title {
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  line-height: 1.2;
}
.block-sub {
  font-size: 0.8rem;
  color: var(--ink-3);
}
.block-actions {
  margin-left: auto;
  display: flex;
  gap: 12px;
}

.topic-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}
@media (max-width: 560px) {
  .topic-grid { grid-template-columns: 1fr; }
}

.topic-card {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 14px 14px;
  border: 1.5px solid var(--line);
  border-radius: 14px;
  background: var(--bg);
  cursor: pointer;
  transition: border-color .15s, background .15s, transform .15s;
  user-select: none;
  text-align: left;
  width: 100%;
  font: inherit;
  color: inherit;
}
.topic-card:hover {
  border-color: var(--ink-3);
  transform: translateY(-1px);
}
.topic-card.selected {
  border-color: var(--accent);
  background: var(--accent-soft);
}
.topic-card .tc-check {
  width: 20px;
  height: 20px;
  border-radius: 6px;
  border: 1.5px solid var(--line);
  background: var(--surface);
  flex-shrink: 0;
  margin-top: 1px;
  display: grid;
  place-items: center;
  transition: all .15s;
}
.topic-card.selected .tc-check {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}
.topic-card .tc-check svg {
  opacity: 0;
  width: 12px;
  height: 12px;
}
.topic-card.selected .tc-check svg { opacity: 1; }
.topic-card .tc-body { flex: 1; min-width: 0; }
.topic-card .tc-name {
  font-weight: 600;
  font-size: 0.9rem;
  line-height: 1.3;
  margin-bottom: 2px;
}
.topic-card .tc-meta {
  font-size: 0.75rem;
  color: var(--ink-3);
}

.settings-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}
@media (max-width: 560px) {
  .settings-grid { grid-template-columns: 1fr; }
}

.setting-card {
  background: var(--bg);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 16px;
}

.preset-row {
  display: flex;
  gap: 6px;
  margin-top: 10px;
  flex-wrap: wrap;
}
.preset-row button {
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink-2);
  font-size: 0.8rem;
  font-weight: 600;
  padding: 6px 12px;
  border-radius: 8px;
  cursor: pointer;
  transition: all .15s;
}
.preset-row button:hover {
  border-color: var(--ink-3);
  color: var(--ink);
}
.preset-row button.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.practice-start {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-top: 8px;
  padding: 16px 18px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: var(--shadow);
  flex-wrap: wrap;
}
.start-summary {
  font-size: 0.9rem;
  color: var(--ink-2);
  flex: 1;
  min-width: 160px;
}
.start-summary strong { color: var(--ink); font-weight: 600; }
.practice-start .btn { min-width: 140px; }

/* Keep old topic-option styles harmless if leftover */
.topic-select { display: none; }

/* 404 Error Page */
.error-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 60vh;
  text-align: center;
  padding: 40px 20px;
}
.error-code {
  font-size: 6rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--accent), var(--bad));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 16px;
  line-height: 1;
}
.error-title {
  font-size: 1.8rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--ink);
}
.error-desc {
  font-size: 1rem;
  color: var(--ink-2);
  margin-bottom: 28px;
  max-width: 400px;
}
.error-container .btn {
  min-width: 150px;
}

/* Visitor Footer */
.visitor-footer {
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
  text-align: center;
}
.visitor-text {
  font-size: 0.9rem;
  color: var(--ink-2);
}