:root {
  --bg: #f4f6fa;
  --card: #ffffff;
  --text: #1f2733;
  --sub: #5b6675;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --ok: #16a34a;
  --ng: #dc2626;
  --warn: #d97706;
  --border: #dfe5ee;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(16, 24, 40, .08);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Yu Gothic", Meiryo, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.75;
}

/* ---------- ヘッダー ---------- */
.topbar {
  background: #10213f;
  color: #fff;
  position: sticky;
  top: 0;
  z-index: 10;
}
.topbar-inner {
  max-width: 860px;
  margin: 0 auto;
  padding: 10px 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
}
.logo { font-weight: 700; font-size: 1.05rem; }
.nav { display: flex; gap: 4px; }
.nav-btn {
  background: transparent;
  border: none;
  color: #c3cfe4;
  padding: 8px 14px;
  border-radius: 8px;
  font-size: .95rem;
  cursor: pointer;
}
.nav-btn:hover { background: rgba(255,255,255,.1); color: #fff; }
.nav-btn.active { background: var(--primary); color: #fff; }

.container { max-width: 860px; margin: 0 auto; padding: 24px 16px 64px; }
.footer {
  text-align: center;
  color: var(--sub);
  font-size: .8rem;
  padding: 24px 16px 40px;
}

/* ---------- ホーム ---------- */
.hero {
  background: linear-gradient(135deg, #1e3a8a, #2563eb);
  color: #fff;
  border-radius: var(--radius);
  padding: 28px 24px;
  margin-bottom: 20px;
}
.hero h2 { margin: 0 0 4px; font-size: 1.5rem; }
.hero-sub { margin: 0; opacity: .85; font-size: .9rem; }
.countdown {
  margin-top: 12px;
  font-size: 1.05rem;
}
.countdown strong { font-size: 1.6rem; }

.stat-cards {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  margin-bottom: 28px;
}
.stat-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  text-align: center;
  padding: 14px 6px;
}
.stat-num { font-size: 1.7rem; font-weight: 700; }
.stat-card.ok .stat-num { color: var(--ok); }
.stat-card.ng .stat-num { color: var(--ng); }
.stat-label { font-size: .8rem; color: var(--sub); }

.section-title { margin: 20px 0 10px; font-size: 1.05rem; }

.unit-list { display: flex; flex-direction: column; gap: 8px; }
.unit-row {
  display: flex;
  align-items: center;
  gap: 12px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 10px 16px;
  cursor: pointer;
  transition: border-color .15s, transform .1s;
}
.unit-row:hover { border-color: var(--primary); transform: translateY(-1px); }
.unit-icon {
  width: 34px; height: 34px;
  border-radius: 8px;
  background: #e8efff;
  color: var(--primary-dark);
  display: flex; align-items: center; justify-content: center;
  font-weight: 700;
  flex-shrink: 0;
}
.unit-icon.big { width: 44px; height: 44px; font-size: 1.2rem; }
.unit-name { flex: 0 0 15em; font-size: .95rem; }
.unit-pct { color: var(--sub); font-size: .85rem; min-width: 3.5em; text-align: right; }

.bar {
  flex: 1;
  height: 8px;
  background: #e5eaf2;
  border-radius: 4px;
  overflow: hidden;
}
.bar-fill { height: 100%; background: var(--ok); border-radius: 4px; transition: width .3s; }

.home-actions { margin-top: 24px; display: flex; gap: 10px; flex-wrap: wrap; }

/* ---------- ボタン ---------- */
.btn {
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--text);
  padding: 10px 18px;
  border-radius: 10px;
  font-size: .95rem;
  cursor: pointer;
  transition: filter .1s, transform .1s;
}
.btn:hover { filter: brightness(.96); transform: translateY(-1px); }
.btn:disabled { opacity: .45; cursor: default; }
.btn-lg { padding: 13px 26px; font-size: 1.05rem; }
.btn-primary { background: var(--primary); border-color: var(--primary); color: #fff; }
.btn-warn { background: #fef3e2; border-color: #f5cf8f; color: var(--warn); }
.btn-ok { background: var(--ok); border-color: var(--ok); color: #fff; }
.btn-ng { background: var(--ng); border-color: var(--ng); color: #fff; }
.btn-ghost { background: transparent; border-color: transparent; color: var(--sub); }
.btn-ghost:hover { color: var(--text); }

/* ---------- クイズメニュー ---------- */
.page-title { margin: 4px 0 8px; }
.page-desc { color: var(--sub); margin: 0 0 16px; }
.quiz-modes { display: flex; gap: 10px; margin-bottom: 20px; flex-wrap: wrap; }
.unit-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 12px;
}
.unit-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 6px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 16px;
  cursor: pointer;
  font-family: inherit;
  text-align: left;
  transition: border-color .15s, transform .1s;
}
.unit-card:hover { border-color: var(--primary); transform: translateY(-2px); }
.unit-card .unit-name { font-size: 1rem; font-weight: 600; flex: none; }
.unit-count { color: var(--sub); font-size: .82rem; }

/* ---------- クイズ画面 ---------- */
.quiz-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-bottom: 8px;
}
.quiz-title { font-weight: 600; }
.quiz-progress { color: var(--sub); font-variant-numeric: tabular-nums; }
.quiz-bar { margin-bottom: 18px; }
.quiz-bar .bar-fill { background: var(--primary); }

.q-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
}
.q-meta { display: flex; gap: 8px; margin-bottom: 12px; }
.tag {
  background: #e8efff;
  color: var(--primary-dark);
  border-radius: 6px;
  padding: 2px 10px;
  font-size: .78rem;
}
.tag.level { background: #f1f5f9; color: var(--sub); }
.q-body { font-size: 1.05rem; }

/* ---------- 4択選択肢 ---------- */
.choices {
  margin-top: 18px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.choice-btn {
  display: flex;
  align-items: center;
  gap: 12px;
  width: 100%;
  min-height: 52px;
  background: var(--card);
  border: 2px solid var(--border);
  border-radius: 12px;
  padding: 12px 14px;
  font-family: inherit;
  font-size: 1rem;
  text-align: left;
  cursor: pointer;
  transition: border-color .15s, background .15s;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
}
.choice-btn:not(:disabled):hover,
.choice-btn:not(:disabled):active { border-color: var(--primary); background: #f5f8ff; }
.choice-btn:disabled { cursor: default; opacity: .75; }
.choice-btn.correct {
  border-color: var(--ok);
  background: #f0fdf4;
  opacity: 1;
}
.choice-btn.wrong {
  border-color: var(--ng);
  background: #fef2f2;
  opacity: 1;
}
.choice-label {
  flex-shrink: 0;
  width: 30px; height: 30px;
  border-radius: 50%;
  background: #eef2f8;
  color: var(--sub);
  display: flex; align-items: center; justify-content: center;
  font-size: .85rem;
  font-weight: 700;
}
.choice-btn.correct .choice-label { background: var(--ok); color: #fff; }
.choice-btn.wrong .choice-label { background: var(--ng); color: #fff; }
.choice-text { flex: 1; overflow-x: auto; }

.verdict {
  margin-top: 18px;
  font-size: 1.15rem;
  font-weight: 700;
  text-align: center;
}
.verdict.v-ok { color: var(--ok); }
.verdict.v-ng { color: var(--ng); }

.exp-box {
  margin-top: 12px;
  border-radius: 10px;
  padding: 14px 18px;
  background: #f8fafc;
  border: 1px solid var(--border);
}
.answer-label { font-size: .8rem; font-weight: 700; color: var(--sub); margin-bottom: 4px; }

.next-row { margin-top: 18px; }
.btn-block { display: block; width: 100%; }

/* ---------- 結果 ---------- */
.result-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  text-align: center;
  padding: 40px 24px;
}
.result-title { color: var(--sub); }
.result-score { font-size: 3.4rem; font-weight: 700; color: var(--primary); }
.result-score .pct { font-size: 1.4rem; }
.result-card .home-actions { justify-content: center; }

/* ---------- ノート ---------- */
.note-tabs {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  margin-bottom: 16px;
}
.note-tab {
  border: 1px solid var(--border);
  background: var(--card);
  border-radius: 999px;
  padding: 6px 14px;
  font-size: .85rem;
  cursor: pointer;
  color: var(--sub);
}
.note-tab.active { background: var(--primary); border-color: var(--primary); color: #fff; }

.note-body {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px 28px;
  overflow-x: auto;
}
.note-body h3 {
  margin: 26px 0 10px;
  padding-left: 10px;
  border-left: 4px solid var(--primary);
  font-size: 1.1rem;
}
.note-body h3:first-child { margin-top: 0; }
.note-body table {
  border-collapse: collapse;
  margin: 10px 0;
  width: 100%;
}
.note-body th, .note-body td,
.q-card th, .q-card td {
  border: 1px solid var(--border);
  padding: 6px 12px;
  text-align: left;
}
.note-body th { background: #f1f5f9; }
.q-card table { border-collapse: collapse; margin: 8px 0; }
.q-card th { background: #f1f5f9; }

/* 数式ブロックのはみ出し対策 */
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }

/* ---------- スマホ最適化 ---------- */
@media (max-width: 640px) {
  body { font-size: 15px; }
  .container { padding: 16px 12px 56px; }
  .topbar-inner { padding: 8px 10px; justify-content: center; }
  .logo { width: 100%; text-align: center; font-size: 1rem; }
  .nav { width: 100%; justify-content: space-between; }
  .nav-btn { padding: 8px 2px; font-size: .82rem; flex: 1; text-align: center; white-space: nowrap; }
  .hero { padding: 20px 16px; }
  .hero h2 { font-size: 1.25rem; }
  .stat-cards { grid-template-columns: repeat(2, 1fr); }
  .unit-name { flex: 1; }
  .unit-row .bar { display: none; }
  .unit-grid { grid-template-columns: 1fr; }
  .q-card { padding: 16px 12px; }
  .q-body { font-size: 1rem; }
  .choice-btn { font-size: .95rem; padding: 12px 10px; }
  .note-body { padding: 16px 12px; }
  .note-body .katex-display .katex { font-size: 1em; }
  .exp-box { padding: 12px 12px; }
  .quiz-title { font-size: .9rem; }
}