:root {
  color-scheme: light;
  --bg: #f8f5ec;
  --surface: #fffdf6;
  --surface-2: #efe7d5;
  --text: #1c2b27;
  --muted: #64746e;
  --line: #ded4bf;
  --primary: #006d77;
  --primary-2: #83c5be;
  --accent: #f4a261;
  --gold: #e9c46a;
  --danger: #b23a48;
  --ok: #2a9d8f;
  --shadow: 0 24px 80px rgba(28, 43, 39, 0.12);
}

body.dark {
  color-scheme: dark;
  --bg: #111a1c;
  --surface: #182528;
  --surface-2: #213236;
  --text: #f4f1e9;
  --muted: #b9c5c1;
  --line: #345056;
  --primary: #7bd7df;
  --primary-2: #235a60;
  --accent: #ffb267;
  --gold: #ffd166;
  --danger: #ff7d87;
  --ok: #74d3c8;
  --shadow: 0 24px 80px rgba(0, 0, 0, 0.28);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Noto Sans CJK TC", "PingFang TC", "Microsoft JhengHei", sans-serif;
  background: radial-gradient(circle at top left, color-mix(in srgb, var(--primary-2) 35%, transparent), transparent 36rem), var(--bg);
  color: var(--text);
  line-height: 1.65;
}

a { color: inherit; }

.skip-link {
  position: absolute;
  left: 1rem;
  top: -4rem;
  background: var(--primary);
  color: var(--surface);
  padding: .7rem 1rem;
  border-radius: 1rem;
  z-index: 10;
}

.skip-link:focus { top: 1rem; }

.hero {
  min-height: 78vh;
  padding: 1.25rem clamp(1rem, 4vw, 4rem) 4rem;
}

.topbar, .tabs, .hero-grid, .section, .footer {
  max-width: 1180px;
  margin: 0 auto;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: .75rem;
  font-weight: 800;
  color: var(--primary);
}

.logo {
  display: grid;
  place-items: center;
  width: 2.6rem;
  height: 2.6rem;
  border: 2px solid currentColor;
  border-radius: .9rem;
}

button, .primary, .secondary, .ghost {
  border: 0;
  border-radius: 999px;
  padding: .85rem 1.2rem;
  font: inherit;
  font-weight: 800;
  cursor: pointer;
  text-decoration: none;
  transition: transform .18s ease, box-shadow .18s ease, background .18s ease;
}

button:hover, .primary:hover, .secondary:hover, .ghost:hover { transform: translateY(-2px); }

.primary {
  display: inline-flex;
  background: var(--primary);
  color: var(--surface);
  box-shadow: var(--shadow);
}

.secondary, .ghost {
  display: inline-flex;
  background: var(--surface);
  color: var(--primary);
  border: 1px solid var(--line);
}

.hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(18rem, .7fr);
  gap: clamp(1.5rem, 5vw, 5rem);
  align-items: center;
  padding-top: 6rem;
}

.eyebrow {
  margin: 0 0 .65rem;
  color: var(--primary);
  font-weight: 900;
  letter-spacing: .08em;
  text-transform: uppercase;
}

h1, h2, h3 { line-height: 1.15; margin: 0; }
h1 { font-size: clamp(2.8rem, 8vw, 6.5rem); letter-spacing: -.06em; max-width: 10ch; }
h2 { font-size: clamp(2rem, 4vw, 3.2rem); letter-spacing: -.04em; }
h3 { font-size: 1.35rem; }

.lede {
  max-width: 46rem;
  color: var(--muted);
  font-size: 1.18rem;
}

.hero-actions, .quiz-actions {
  display: flex;
  flex-wrap: wrap;
  gap: .8rem;
  margin-top: 1.5rem;
}

.hero-card, .concept, .tool-card, .source-card, .result-card, .drill, .mistake, .question-card, .exam-type-card {
  background: color-mix(in srgb, var(--surface) 94%, transparent);
  border: 1px solid var(--line);
  border-radius: 2rem;
  padding: 1.5rem;
  box-shadow: var(--shadow);
}

.hero-card {
  transform: rotate(1deg);
  border: 2px solid var(--gold);
}

.hero-card p { color: var(--primary); font-weight: 900; margin-top: 0; }

.tabs {
  position: sticky;
  top: .75rem;
  z-index: 5;
  display: flex;
  gap: .5rem;
  overflow-x: auto;
  padding: .75rem;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: blur(16px);
  border: 1px solid var(--line);
  border-radius: 999px;
}

.tabs a {
  white-space: nowrap;
  text-decoration: none;
  border-radius: 999px;
  padding: .65rem .95rem;
  color: var(--muted);
  font-weight: 800;
}

.tabs a:hover { background: var(--surface-2); color: var(--text); }

.section { padding: 5rem clamp(1rem, 3vw, 2rem); }
.section.alt { background: color-mix(in srgb, var(--surface-2) 35%, transparent); border-radius: 3rem; }
.section-head { max-width: 55rem; margin-bottom: 2rem; }
.section-head p:last-child { color: var(--muted); font-size: 1.08rem; }

.concept-grid, .tool-grid, .mistake-grid, .exam-grid, .audio-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.concept {
  position: relative;
  overflow: hidden;
}

.audio-section {
  background:
    linear-gradient(135deg, color-mix(in srgb, var(--primary-2) 20%, transparent), transparent 45%),
    color-mix(in srgb, var(--surface) 86%, transparent);
  border-radius: 3rem;
}

.audio-toolbar {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: .8rem;
  margin-bottom: 1.25rem;
}

.audio-status {
  color: var(--muted);
  font-weight: 800;
}

.audio-card {
  background: color-mix(in srgb, var(--surface) 94%, transparent);
  border: 1px solid var(--line);
  border-radius: 1.6rem;
  padding: 1.4rem;
  box-shadow: var(--shadow);
}

.audio-card h3 {
  color: var(--primary);
}

.audio-card.speaking {
  outline: 3px solid var(--gold);
  background: color-mix(in srgb, var(--gold) 18%, var(--surface));
}

.listen-btn {
  margin-top: .6rem;
  background: var(--surface-2);
  color: var(--primary);
}

.read-aloud,
.question-audio,
.stop-speaking {
  display: inline-flex;
  align-items: center;
  gap: .35rem;
  margin-top: .75rem;
  padding: .55rem .85rem;
  border-radius: 999px;
  background: color-mix(in srgb, var(--primary-2) 24%, var(--surface));
  color: var(--primary);
  border: 1px solid color-mix(in srgb, var(--primary) 32%, var(--line));
  font-size: .92rem;
  font-weight: 900;
}

.stop-speaking {
  margin-left: .45rem;
  background: var(--surface);
  color: var(--primary);
  border-color: var(--line);
}

.stop-speaking:hover {
  background: color-mix(in srgb, var(--danger) 8%, var(--surface));
  border-color: color-mix(in srgb, var(--danger) 32%, var(--line));
}

.section-read-row {
  margin-top: 1rem;
  display: flex;
  flex-wrap: wrap;
  gap: .55rem;
  align-items: center;
}

.speaking-now {
  outline: 3px solid var(--gold);
  background: color-mix(in srgb, var(--gold) 13%, var(--surface)) !important;
}

.audio-note {
  color: var(--muted);
  margin-top: 1rem;
  font-weight: 700;
}

.badge {
  display: inline-grid;
  place-items: center;
  width: 2.2rem;
  height: 2.2rem;
  border-radius: 50%;
  background: var(--gold);
  color: #2b2109;
  font-weight: 900;
  margin-bottom: .8rem;
}

.tool-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }

input, select {
  width: 100%;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--text);
  border-radius: 1rem;
  padding: .8rem;
  font: inherit;
}

.form-row, .triple-input {
  display: grid;
  grid-template-columns: 1fr 1fr auto 1fr;
  gap: .6rem;
  align-items: center;
  margin: 1rem 0;
}

.triple-input { grid-template-columns: repeat(3, 1fr); }
.triple-input.compact { grid-template-columns: repeat(5, 1fr); }
label { color: var(--muted); font-weight: 800; font-size: .9rem; }

.answer-box {
  display: block;
  min-height: 4rem;
  background: color-mix(in srgb, var(--primary-2) 24%, var(--surface));
  border: 1px solid color-mix(in srgb, var(--primary) 30%, var(--line));
  border-radius: 1.25rem;
  padding: 1rem;
  font-weight: 850;
}

.mistake h3 { color: var(--primary); }
.mistake .wrong { color: var(--danger); font-weight: 900; }
.mistake .right { color: var(--ok); font-weight: 900; }
.mini-question { margin-top: 1rem; border-top: 1px solid var(--line); padding-top: 1rem; }
.mini-question-list { display: grid; gap: .85rem; }
.mini-options { display: grid; gap: .5rem; margin-top: .7rem; }
.mini-options button { text-align: left; border-radius: 1rem; background: var(--surface-2); color: var(--text); font-weight: 700; }
.mini-options button.correct { background: color-mix(in srgb, var(--ok) 35%, var(--surface)); }
.mini-options button.wrong { background: color-mix(in srgb, var(--danger) 22%, var(--surface)); }
.instant-feedback,
.quiz-feedback {
  margin-top: .75rem;
  padding: .85rem 1rem;
  border-radius: 1rem;
  font-weight: 800;
  line-height: 1.65;
}
.instant-feedback.correct,
.quiz-feedback.correct {
  color: color-mix(in srgb, var(--ok) 80%, var(--text));
  background: color-mix(in srgb, var(--ok) 16%, var(--surface));
  border: 1px solid color-mix(in srgb, var(--ok) 42%, var(--line));
}
.instant-feedback.wrong,
.quiz-feedback.wrong {
  color: color-mix(in srgb, var(--danger) 82%, var(--text));
  background: color-mix(in srgb, var(--danger) 12%, var(--surface));
  border: 1px solid color-mix(in srgb, var(--danger) 36%, var(--line));
}

.checklist { padding-left: 1.2rem; }
.checklist li { margin: .7rem 0; }
.check-btn { padding: .45rem .75rem; margin-right: .4rem; background: var(--gold); color: #2b2109; }
.check-btn.done { background: var(--ok); color: white; }

.sources { padding-left: 1.2rem; }
.sources a { color: var(--primary); font-weight: 800; }

.exam-type-panel {
  margin-top: 1.2rem;
  padding: 1.4rem;
  border: 1px solid var(--line);
  border-radius: 2rem;
  background: color-mix(in srgb, var(--surface) 72%, transparent);
}

.exam-type-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.exam-type-card {
  box-shadow: none;
  border-radius: 1.5rem;
}

.type-badge {
  display: inline-flex;
  width: fit-content;
  border-radius: 999px;
  padding: .35rem .7rem;
  background: color-mix(in srgb, var(--primary) 14%, var(--surface));
  color: var(--primary);
  font-weight: 900;
}

.exam-practice-list {
  display: grid;
  gap: .75rem;
  margin-top: 1rem;
}

.exam-practice {
  padding: .85rem;
  border-radius: 1rem;
  background: var(--surface-2);
}

.practice-question {
  margin-top: 0;
  font-weight: 900;
}

.exam-answer-input {
  width: 100%;
  margin: .65rem 0;
  padding: .75rem .85rem;
  border-radius: .85rem;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--text);
  font: inherit;
  font-weight: 700;
}

.exam-answer-input:focus {
  outline: 3px solid color-mix(in srgb, var(--primary) 28%, transparent);
  border-color: var(--primary);
}

.check-exam-answer {
  background: var(--gold);
  color: #2b2109;
  padding: .55rem .85rem;
  margin-right: .5rem;
}

.exam-feedback {
  margin: .7rem 0;
  padding: .75rem .85rem;
  border-radius: .9rem;
  font-weight: 800;
  line-height: 1.55;
}

.exam-feedback.correct {
  color: color-mix(in srgb, var(--ok) 82%, var(--text));
  background: color-mix(in srgb, var(--ok) 14%, var(--surface));
  border: 1px solid color-mix(in srgb, var(--ok) 38%, var(--line));
}

.exam-feedback.wrong {
  color: color-mix(in srgb, var(--danger) 82%, var(--text));
  background: color-mix(in srgb, var(--danger) 12%, var(--surface));
  border: 1px solid color-mix(in srgb, var(--danger) 36%, var(--line));
}

.reveal-answer {
  background: var(--primary);
  color: white;
  padding: .55rem .85rem;
}

.practice-answer {
  margin-top: .7rem;
  padding: .8rem;
  border-radius: .9rem;
  background: color-mix(in srgb, var(--ok) 12%, var(--surface));
  border: 1px solid color-mix(in srgb, var(--ok) 34%, var(--line));
}

.trap-sentence {
  padding: 1rem;
  margin: .75rem 0;
  border-radius: 1.2rem;
  background: var(--surface);
  border: 1px solid var(--line);
}
.trap-word {
  border: 0;
  background: transparent;
  padding: .25rem .35rem;
  border-radius: .6rem;
  color: var(--text);
  font-weight: 800;
}
.trap-word.hit { background: var(--gold); color: #2b2109; }

.quiz-list { display: grid; gap: 1rem; }
.question-card label {
  display: block;
  background: var(--surface-2);
  color: var(--text);
  border-radius: 1rem;
  padding: .75rem;
  margin: .5rem 0;
  border: 1px solid transparent;
}
.question-card label.correct-choice {
  background: color-mix(in srgb, var(--ok) 22%, var(--surface));
  border-color: color-mix(in srgb, var(--ok) 48%, var(--line));
}
.question-card label.wrong-choice {
  background: color-mix(in srgb, var(--danger) 15%, var(--surface));
  border-color: color-mix(in srgb, var(--danger) 45%, var(--line));
}
.question-card.correct { border-color: var(--ok); }
.question-card.incorrect { border-color: var(--danger); }
.explain { color: var(--muted); font-weight: 700; }
.result-card { display: none; margin-top: 1rem; }
.result-card.show { display: block; }

.gallery-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
}
.gallery-item {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 1.25rem;
  overflow: hidden;
}
.gallery-item img {
  display: block;
  width: 100%;
  aspect-ratio: 4 / 5;
  object-fit: cover;
}
.gallery-item p { margin: .7rem .9rem 1rem; color: var(--muted); font-weight: 800; }

.footer {
  padding: 3rem 1rem;
  color: var(--muted);
  text-align: center;
}

@media (max-width: 820px) {
  .hero { padding-inline: 1rem; }
  .hero-grid, .concept-grid, .tool-grid, .mistake-grid, .exam-grid, .audio-grid, .exam-type-grid { grid-template-columns: 1fr; }
  .hero-grid { padding-top: 3rem; }
  .section, .section.alt { border-radius: 0; padding-block: 3.5rem; }
  .form-row, .triple-input, .triple-input.compact { grid-template-columns: 1fr; }
  .gallery-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  h1 { max-width: 9ch; }
}

@media (max-width: 480px) {
  .gallery-grid { grid-template-columns: 1fr; }
  .topbar { align-items: flex-start; }
  .brand { font-size: .95rem; }
}