:root {
  --bg: #F4F0E8;
  --bg-deep: #EBE5D8;
  --surface: #FFFFFF;
  --surface-2: #FAF7F0;
  --border: #E6DFCF;
  --border-soft: #EFE9DB;
  --ink: #33291E;
  --ink-dim: #8A8070;
  --ink-faint: #B3AA98;
  --accent: #C96442;
  --accent-hover: #B4552F;
  --accent-soft: #F2DFCF;
  --accent-soft-2: #FBEFE4;
  --accent-ink: #8C4123;
  --good: #4F7A5B;
  --good-bg: #E6EEE4;
  --bad: #B23B2E;
  --bad-bg: #F5E3DE;
  --radius-lg: 20px;
  --radius-md: 14px;
  --radius-sm: 10px;
  --shadow-card: 0 1px 2px rgba(51, 41, 30, 0.04), 0 6px 16px -8px rgba(51, 41, 30, 0.10);
  --shadow-card-hover: 0 2px 4px rgba(51, 41, 30, 0.06), 0 12px 28px -10px rgba(201, 100, 66, 0.22);
  --font-display: "Fraunces", "Noto Serif SC", Georgia, serif;
  --font-cjk-display: "Noto Serif SC", "Fraunces", Georgia, serif;
  --font-body: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-body);
  min-height: 100vh;
}

.paper-texture {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background:
    radial-gradient(1100px 620px at 12% -8%, rgba(201, 100, 66, 0.10), transparent 60%),
    radial-gradient(900px 560px at 108% 12%, rgba(201, 100, 66, 0.07), transparent 55%),
    var(--bg);
}
.paper-texture::after {
  content: "";
  position: absolute;
  inset: 0;
  opacity: 0.5;
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='120' height='120'><filter id='n'><feTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='2' stitchTiles='stitch'/><feColorMatrix type='saturate' values='0'/></filter><rect width='100%25' height='100%25' filter='url(%23n)' opacity='0.035'/></svg>");
}

#app {
  position: relative;
  z-index: 1;
  max-width: 720px;
  margin: 0 auto;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  padding: 0 20px 40px;
}

.screen { flex: 1; display: flex; flex-direction: column; }
.hidden { display: none !important; }

/* Level 1: app shell header */
.app-shell-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 22px 0 18px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  cursor: pointer;
  user-select: none;
}
.brand-mark {
  color: var(--accent);
  display: inline-flex;
  transition: transform 0.35s ease;
}
.brand:hover .brand-mark { transform: rotate(24deg); }
.brand-word {
  font-family: var(--font-cjk-display);
  font-weight: 700;
  font-size: 17px;
  letter-spacing: 0.02em;
  color: var(--ink);
}

.crumb {
  font-size: 13px;
  color: var(--ink-faint);
}

.app-main { flex: 1; display: flex; flex-direction: column; }

/* Level 2: subject menu */
.hero { margin: 8px 0 26px; }
.hero h1 {
  font-family: var(--font-cjk-display);
  font-weight: 600;
  font-size: 27px;
  line-height: 1.35;
  margin: 0 0 10px;
  color: var(--ink);
}
.hero-sub {
  margin: 0;
  font-size: 14px;
  color: var(--ink-dim);
  line-height: 1.6;
}

.subject-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.subject-item {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 15px 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-card);
  cursor: pointer;
  text-align: left;
  transition: border-color 0.18s ease, box-shadow 0.18s ease, transform 0.12s ease;
}
.subject-item:hover {
  border-color: var(--accent);
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-1px);
}
.subject-item:active { transform: translateY(0); }

.subject-icon {
  flex-shrink: 0;
  width: 42px;
  height: 42px;
  border-radius: 12px;
  background: var(--accent-soft);
  color: var(--accent-ink);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 19px;
}

.subject-info { flex: 1; min-width: 0; }
.subject-name {
  font-size: 15.5px;
  font-weight: 600;
  color: var(--ink);
  margin-bottom: 2px;
}
.subject-meta {
  font-size: 12.5px;
  color: var(--ink-faint);
}

.subject-chevron {
  flex-shrink: 0;
  color: var(--ink-faint);
  font-size: 18px;
  transition: transform 0.18s ease, color 0.18s ease;
}
.subject-item:hover .subject-chevron { transform: translateX(2px); color: var(--accent); }

/* Level 3: source / type / order */
.back-link {
  align-self: flex-start;
  background: none;
  border: none;
  color: var(--ink-dim);
  font-size: 14px;
  cursor: pointer;
  padding: 4px 0 14px;
}
.back-link:hover { color: var(--accent); }

.subject-title {
  font-family: var(--font-cjk-display);
  font-weight: 600;
  font-size: 24px;
  margin: 0 0 4px;
  color: var(--ink);
}
.subject-count {
  margin: 0 0 22px;
  font-size: 13px;
  color: var(--ink-faint);
}

.setup-card {
  background: var(--surface);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-md);
  padding: 16px 16px 14px;
  margin-bottom: 14px;
  box-shadow: var(--shadow-card);
}

.setup-label {
  font-size: 12.5px;
  color: var(--ink-dim);
  margin-bottom: 10px;
  font-weight: 600;
  letter-spacing: 0.03em;
}

.chip-group {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.chip {
  position: relative;
  display: inline-flex;
  align-items: center;
  padding: 8px 15px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 999px;
  font-size: 13.5px;
  color: var(--ink);
  cursor: pointer;
  user-select: none;
  transition: all 0.15s ease;
}

.chip input {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
}

.chip:has(input:checked) {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--accent-ink);
  font-weight: 600;
}

.chip:hover { border-color: var(--accent); }

.setup-summary {
  margin: 4px 0 20px;
  font-size: 13px;
  color: var(--ink-dim);
  background: var(--surface-2);
  border: 1px dashed var(--border);
  border-radius: var(--radius-sm);
  padding: 12px 16px;
}

.primary-btn {
  background: var(--accent);
  color: #FFF9F4;
  border: none;
  border-radius: 999px;
  padding: 15px 20px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 8px 20px -8px rgba(201, 100, 66, 0.55);
  transition: background 0.15s ease, transform 0.05s ease, box-shadow 0.15s ease;
}
.primary-btn:hover { background: var(--accent-hover); box-shadow: 0 10px 24px -8px rgba(201, 100, 66, 0.65); }
.primary-btn:active { transform: scale(0.98); }
.primary-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  box-shadow: none;
}

.secondary-btn {
  background: var(--surface);
  color: var(--ink);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 15px 20px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: border-color 0.15s ease;
}
.secondary-btn:hover { border-color: var(--accent); color: var(--accent-ink); }

.text-btn {
  background: none;
  border: none;
  color: var(--ink-dim);
  font-size: 14px;
  cursor: pointer;
  padding: 6px 4px;
}
.text-btn:hover { color: var(--accent-ink); }

/* Quiz screen */
.quiz-header {
  display: flex;
  align-items: center;
  gap: 14px;
  margin: 6px 0 22px;
}

.progress-wrap { flex: 1; }

.progress-bar {
  height: 6px;
  background: var(--bg-deep);
  border-radius: 999px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--accent);
  width: 0%;
  transition: width 0.25s ease;
}

.progress-text {
  font-size: 12px;
  color: var(--ink-faint);
  margin-top: 6px;
}

.score-text {
  font-size: 13px;
  color: var(--ink-dim);
  white-space: nowrap;
}

.quiz-body { flex: 1; }

.q-source {
  font-size: 12px;
  color: var(--ink-faint);
  margin-bottom: 10px;
  letter-spacing: 0.02em;
}

.q-text {
  font-family: var(--font-cjk-display);
  font-size: 19px;
  line-height: 1.6;
  font-weight: 600;
  margin-bottom: 20px;
  color: var(--ink);
}

.q-options {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.option {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 14px 16px;
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-md);
  cursor: pointer;
  font-size: 15px;
  line-height: 1.5;
  box-shadow: var(--shadow-card);
  transition: border-color 0.15s ease, background 0.15s ease, transform 0.1s ease;
}

.option:hover:not(.disabled) { border-color: var(--accent); transform: translateY(-1px); }

.option-label {
  flex-shrink: 0;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: var(--surface-2);
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 13px;
  font-weight: 700;
  color: var(--ink-dim);
}

.option.correct {
  border-color: var(--good);
  background: var(--good-bg);
}
.option.correct .option-label { background: var(--good); border-color: var(--good); color: #F4FAF3; }

.option.incorrect {
  border-color: var(--bad);
  background: var(--bad-bg);
}
.option.incorrect .option-label { background: var(--bad); border-color: var(--bad); color: #FCF1EE; }

.option.disabled { cursor: default; }
.option.disabled:hover { transform: none; }
.option.dim { opacity: 0.5; }

.matching-box {
  display: flex;
  gap: 14px;
}

.matching-col {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.matching-item {
  padding: 12px 14px;
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 14px;
  cursor: pointer;
  box-shadow: var(--shadow-card);
  transition: border-color 0.15s ease, background 0.15s ease;
}
.matching-item:hover:not(.disabled) { border-color: var(--accent); }
.matching-item.active { border-color: var(--accent); background: var(--accent-soft-2); }
.matching-item.paired { border-style: dashed; color: var(--ink-dim); }
.matching-item.correct { border-color: var(--good); background: var(--good-bg); color: var(--ink); }
.matching-item.incorrect { border-color: var(--bad); background: var(--bad-bg); color: var(--ink); }
.matching-item.disabled { cursor: default; }

.recall-reveal {
  background: var(--surface);
  border: 1.5px dashed var(--border);
  border-radius: var(--radius-lg);
  padding: 18px;
  text-align: center;
  cursor: pointer;
  color: var(--ink-dim);
  font-size: 14px;
}
.recall-reveal:hover { border-color: var(--accent); color: var(--accent-ink); }

.feedback {
  margin-top: 20px;
  padding: 16px 18px;
  border-radius: var(--radius-md);
  border: 1.5px solid var(--border);
  background: var(--surface);
  box-shadow: var(--shadow-card);
}
.feedback.is-correct { border-color: var(--good); background: var(--good-bg); }
.feedback.is-wrong { border-color: var(--bad); background: var(--bad-bg); }

.feedback-title {
  font-family: var(--font-cjk-display);
  font-weight: 700;
  font-size: 15px;
  margin-bottom: 6px;
}
.feedback.is-correct .feedback-title { color: var(--good); }
.feedback.is-wrong .feedback-title { color: var(--bad); }

.feedback-answer {
  font-size: 14px;
  color: var(--ink);
  margin-bottom: 10px;
}

.feedback-explanation {
  font-size: 14px;
  line-height: 1.6;
  color: var(--ink-dim);
}
.feedback-explanation strong { color: var(--ink); font-weight: 700; }

.quiz-footer {
  margin-top: 24px;
  display: flex;
  justify-content: flex-end;
}

/* Result screen */
.result-heading {
  font-family: var(--font-cjk-display);
  font-weight: 600;
  font-size: 26px;
  margin: 8px 0 20px;
  color: var(--ink);
}

.result-score {
  font-family: var(--font-display);
  font-size: 46px;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--accent-ink);
}

.result-detail {
  color: var(--ink-dim);
  font-size: 14px;
  margin-bottom: 28px;
}

.result-actions {
  display: flex;
  gap: 10px;
}
.result-actions button { flex: 1; }

/* Footer */
.app-footer {
  position: relative;
  z-index: 1;
  margin-top: auto;
  padding-top: 20px;
  text-align: center;
  max-width: 720px;
  margin-left: auto;
  margin-right: auto;
  padding-left: 20px;
  padding-right: 20px;
}

.app-footer p {
  margin: 4px 0;
  font-size: 11px;
  line-height: 1.6;
  color: var(--ink-faint);
}

.app-footer a {
  color: var(--ink-dim);
  text-decoration: underline;
}
.app-footer a:hover { color: var(--accent); }

.app-footer .disclaimer { opacity: 0.9; }
.app-footer .warn { color: var(--bad); }

@media (max-width: 480px) {
  #app { padding: 0 14px 30px; }
  .hero h1 { font-size: 23px; }
  .q-text { font-size: 17px; }
}