:root {
  --bg: #f6f5f1;
  --surface: #ffffff;
  --surface-2: #f0eee7;
  --border: #e2ddd0;
  --text: #232019;
  --text-muted: #6b6559;
  --accent: #2f6f4f;
  --accent-2: #b5793a;
  --danger: #b3452f;
  --shadow: 0 1px 2px rgba(30, 27, 18, 0.06), 0 8px 24px rgba(30, 27, 18, 0.06);
  --radius: 14px;
  --font: "Pretendard", "Apple SD Gothic Neo", "Malgun Gothic", -apple-system, BlinkMacSystemFont, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #17160f;
    --surface: #201f19;
    --surface-2: #2a2820;
    --border: #3a382d;
    --text: #ece7da;
    --text-muted: #a39d8b;
    --accent: #6fbf94;
    --accent-2: #d9a15f;
    --danger: #e28066;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 8px 24px rgba(0, 0, 0, 0.35);
  }
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
}

body {
  min-height: 100vh;
  padding: 24px 16px 64px;
}

.wrap {
  max-width: 880px;
  margin: 0 auto;
}

a { color: inherit; }

header.site {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 28px;
  flex-wrap: wrap;
}

header.site h1 {
  font-size: 1.5rem;
  margin: 0;
  letter-spacing: -0.01em;
}

header.site .subtitle {
  color: var(--text-muted);
  font-size: 0.9rem;
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.9rem;
  color: var(--text-muted);
  text-decoration: none;
  margin-bottom: 16px;
}
.back-link:hover { color: var(--text); }

/* Deck grid on home page */
.deck-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 14px;
}

.deck-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
  text-decoration: none;
  color: var(--text);
  box-shadow: var(--shadow);
  transition: transform 0.15s ease, border-color 0.15s ease;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.deck-card:hover { transform: translateY(-2px); border-color: var(--accent); }

.deck-card .chapter-tag {
  font-size: 0.75rem;
  color: var(--accent);
  font-weight: 600;
  letter-spacing: 0.02em;
}

.deck-card h3 {
  margin: 0;
  font-size: 1.1rem;
}

.deck-card .count {
  color: var(--text-muted);
  font-size: 0.85rem;
}

button.deck-card {
  width: 100%;
  text-align: left;
  cursor: pointer;
  font-family: var(--font);
  appearance: none;
}

.deck-card .breakdown {
  color: var(--text-muted);
  font-size: 0.78rem;
  margin-top: -4px;
}

.empty-note {
  color: var(--text-muted);
  border: 1px dashed var(--border);
  border-radius: var(--radius);
  padding: 20px;
  text-align: center;
  font-size: 0.9rem;
}

/* Mode tabs */
.mode-tabs {
  display: flex;
  gap: 6px;
  margin-bottom: 20px;
  background: var(--surface-2);
  padding: 4px;
  border-radius: 10px;
  width: fit-content;
}

.mode-tabs button {
  border: none;
  background: transparent;
  color: var(--text-muted);
  padding: 8px 14px;
  border-radius: 8px;
  font-size: 0.88rem;
  font-family: var(--font);
  cursor: pointer;
}

.mode-tabs button.active {
  background: var(--surface);
  color: var(--text);
  box-shadow: var(--shadow);
  font-weight: 600;
}

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

/* Flashcard mode */
.card-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 14px;
  flex-wrap: wrap;
}

.card-progress {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.toolbar-buttons {
  display: flex;
  gap: 8px;
}

button.chip {
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  padding: 6px 12px;
  border-radius: 999px;
  font-size: 0.82rem;
  font-family: var(--font);
  cursor: pointer;
}
button.chip:hover { border-color: var(--accent); }
button.chip.on { background: var(--accent); color: #fff; border-color: var(--accent); }

.flash-scene {
  perspective: 1400px;
  margin: 0 auto 20px;
  max-width: 560px;
}

.flashcard {
  position: relative;
  min-height: 300px;
  border-radius: var(--radius);
  cursor: pointer;
  transform-style: preserve-3d;
  transition: transform 0.45s cubic-bezier(.2,.8,.2,1);
}

.flashcard.flipped { transform: rotateY(180deg); }

.flash-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  padding: 28px 24px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  overflow-y: auto;
}

.flash-face.back { transform: rotateY(180deg); text-align: left; align-items: stretch; justify-content: flex-start; }

.flash-face .eyebrow {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  margin-bottom: 10px;
  font-weight: 600;
}

.flash-face .main-text {
  font-size: 1.6rem;
  font-weight: 700;
}

.flash-face .sub-text {
  margin-top: 8px;
  color: var(--text-muted);
  font-style: italic;
}

.flash-face .hint {
  margin-top: 18px;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.info-block { margin-bottom: 12px; }
.info-block .label {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 4px;
}
.info-block .value { font-size: 0.92rem; line-height: 1.45; }
.info-block ul { margin: 2px 0 0; padding-left: 18px; }
.info-block li { margin-bottom: 2px; }

.card-image {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  border-radius: 10px;
  border: 1px solid var(--border);
  margin: 4px 0 12px;
}

.special-block {
  background: color-mix(in srgb, var(--accent-2) 14%, transparent);
  border: 1px solid color-mix(in srgb, var(--accent-2) 40%, transparent);
  border-radius: 10px;
  padding: 10px 12px;
  margin-top: 4px;
}
.special-block .label { color: var(--accent-2); }

.nav-buttons {
  display: flex;
  justify-content: center;
  gap: 10px;
}

button.primary {
  background: var(--accent);
  color: #fff;
  border: none;
  padding: 10px 20px;
  border-radius: 10px;
  font-family: var(--font);
  font-size: 0.92rem;
  cursor: pointer;
}
button.primary:hover { filter: brightness(1.08); }
button.secondary {
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border);
  padding: 10px 20px;
  border-radius: 10px;
  font-family: var(--font);
  font-size: 0.92rem;
  cursor: pointer;
}

/* Matching game */
.match-toolbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 14px;
  flex-wrap: wrap;
  gap: 8px;
}

.match-stats { font-size: 0.85rem; color: var(--text-muted); }

.match-board {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

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

.match-item {
  border: 1px solid var(--border);
  background: var(--surface);
  border-radius: 10px;
  padding: 12px 14px;
  font-size: 0.92rem;
  cursor: pointer;
  text-align: left;
  font-family: var(--font);
  color: var(--text);
}
.match-col .match-item:nth-child(1) { font-style: normal; }
.match-col.right .match-item { font-style: italic; }

.match-item.selected { border-color: var(--accent); background: color-mix(in srgb, var(--accent) 12%, var(--surface)); }
.match-item.correct { border-color: var(--accent); background: color-mix(in srgb, var(--accent) 20%, var(--surface)); opacity: 0.55; cursor: default; }
.match-item.wrong { border-color: var(--danger); background: color-mix(in srgb, var(--danger) 18%, var(--surface)); animation: shake 0.3s; }

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

.match-complete {
  text-align: center;
  padding: 40px 20px;
}
.match-complete .big { font-size: 1.3rem; font-weight: 700; margin-bottom: 8px; }

/* Table view */
table.ref-table {
  width: 100%;
  border-collapse: collapse;
  background: var(--surface);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
  font-size: 0.85rem;
}
table.ref-table th, table.ref-table td {
  border: 1px solid var(--border);
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
}
table.ref-table th {
  background: var(--surface-2);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--text-muted);
}
table.ref-table td.sci { font-style: italic; }
table.ref-table .special-tag {
  display: inline-block;
  margin-top: 4px;
  font-size: 0.72rem;
  color: var(--accent-2);
  font-weight: 600;
}

.table-scroll { overflow-x: auto; }

/* Exam mode */
.exam-section-title {
  font-size: 1.05rem;
  font-weight: 700;
  margin: 28px 0 12px;
  padding-bottom: 6px;
  border-bottom: 2px solid var(--border);
}
.exam-section-title:first-child { margin-top: 0; }

.exam-q {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 18px;
  margin-bottom: 12px;
}
.exam-q .q-num {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-weight: 600;
  margin-bottom: 4px;
}
.exam-q .q-text {
  font-size: 0.98rem;
  margin-bottom: 12px;
  line-height: 1.5;
}

.category-filter {
  flex-wrap: wrap;
  margin-bottom: 18px;
  position: sticky;
  top: 0;
  background: var(--bg);
  padding: 6px 0;
  z-index: 5;
}

.exam-q .q-tag {
  display: inline-block;
  font-size: 0.7rem;
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 12%, transparent);
  border-radius: 999px;
  padding: 2px 9px;
  margin-bottom: 6px;
  font-weight: 600;
}

.exam-q.graded.correct { border-color: var(--accent); background: color-mix(in srgb, var(--accent) 8%, var(--surface)); }
.exam-q.graded.wrong { border-color: var(--danger); background: color-mix(in srgb, var(--danger) 7%, var(--surface)); }

.choice-list { display: flex; flex-direction: column; gap: 8px; }
.choice-item {
  display: flex;
  align-items: center;
  gap: 8px;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 12px;
  cursor: pointer;
  font-size: 0.9rem;
}
.choice-item:hover { border-color: var(--accent); }
.choice-item input { accent-color: var(--accent); }
.choice-item.picked { border-color: var(--accent); }
.choice-item.correct-choice { border-color: var(--accent); background: color-mix(in srgb, var(--accent) 15%, var(--surface)); }
.choice-item.wrong-choice { border-color: var(--danger); background: color-mix(in srgb, var(--danger) 12%, var(--surface)); }

.match-select, .short-input {
  width: 100%;
  font-family: var(--font);
  font-size: 0.9rem;
  padding: 8px 10px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
}

.match-row {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 8px;
}
.match-row .m-name { min-width: 130px; font-weight: 600; }
.match-row .m-icon { width: 18px; text-align: center; font-size: 0.9rem; }

.feedback-line {
  margin-top: 10px;
  font-size: 0.85rem;
  color: var(--text-muted);
}
.feedback-line.correct { color: var(--accent); }
.feedback-line.wrong { color: var(--danger); }

.score-summary {
  position: sticky;
  bottom: 12px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 14px 18px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 20px;
}
.score-summary .total { font-weight: 700; font-size: 1.05rem; }

/* PDF viewer */
.pdf-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 12px;
  flex-wrap: wrap;
}
.pdf-toolbar .pdf-name { font-size: 0.85rem; color: var(--text-muted); }
.pdf-frame {
  width: 100%;
  height: 80vh;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
}

@media (max-width: 640px) {
  .match-board { grid-template-columns: 1fr; }
  .flash-face .main-text { font-size: 1.3rem; }
  .match-row { flex-wrap: wrap; }
}