/* =========================================================
   Claude Code 101 — 챕터 공통 테마 (라이트 기본 / 다크 지원)
   ========================================================= */

/* ── Light (기본) ── */
:root {
  --bg: #f8fafc;
  --surface: #ffffff;
  --surface-raised: #f1f5f9;
  --surface-hover: #e8f0f8;
  --border: #e2e8f0;
  --border-bright: #cbd5e1;
  --text: #0f172a;
  --text-dim: #475569;
  --text-muted: #94a3b8;
  --accent: #7c3aed;
  --accent-dim: #6d28d9;
  --accent-glow: rgba(124, 58, 237, 0.10);
  --accent-glow-strong: rgba(124, 58, 237, 0.16);
  --green: #16a34a;
  --green-dim: rgba(22, 163, 74, 0.10);
  --blue: #0284c7;
  --blue-dim: rgba(2, 132, 199, 0.10);
  --orange: #ea580c;
  --orange-dim: rgba(234, 88, 12, 0.10);
  --pink: #be185d;
  --pink-dim: rgba(190, 24, 93, 0.10);
  --yellow: #b45309;
  --yellow-dim: rgba(180, 83, 9, 0.10);
  --shadow-card: 0 2px 12px rgba(0,0,0,.08);
  --shadow-md: 0 8px 32px rgba(0,0,0,.12);
  --nav-bg: rgba(255, 255, 255, 0.90);
  --red: #dc2626;
  --red-dim: rgba(220, 38, 38, 0.08);
  --red-border: rgba(220, 38, 38, 0.18);
  --accent-border: rgba(124, 58, 237, 0.20);
  --green-border: rgba(22, 163, 74, 0.20);
  --blue-border: rgba(2, 132, 199, 0.20);
  --orange-border: rgba(234, 88, 12, 0.20);
  --pink-border: rgba(190, 24, 93, 0.20);
  --yellow-border: rgba(180, 83, 9, 0.20);
}

/* ── Dark ── */
[data-theme="dark"] {
  --bg: #0a0a0f;
  --surface: #12121a;
  --surface-raised: #1a1a26;
  --surface-hover: #22222f;
  --border: #2a2a3a;
  --border-bright: #3a3a5a;
  --text: #e8e8f0;
  --text-dim: #8888a0;
  --text-muted: #5a5a72;
  --accent: #c4a0ff;
  --accent-dim: #9070cc;
  --accent-glow: rgba(196, 160, 255, 0.15);
  --accent-glow-strong: rgba(196, 160, 255, 0.25);
  --green: #7dd3a0;
  --green-dim: rgba(125, 211, 160, 0.12);
  --blue: #7daed3;
  --blue-dim: rgba(125, 174, 211, 0.12);
  --orange: #d3a07d;
  --orange-dim: rgba(211, 160, 125, 0.12);
  --pink: #d37da0;
  --pink-dim: rgba(211, 125, 160, 0.12);
  --yellow: #d3cc7d;
  --yellow-dim: rgba(211, 204, 125, 0.12);
  --shadow-card: 0 2px 12px rgba(0,0,0,.4);
  --shadow-md: 0 8px 32px rgba(0,0,0,.5);
  --nav-bg: rgba(10, 10, 15, 0.85);
  --red: #f87171;
  --red-dim: rgba(248, 113, 113, 0.10);
  --red-border: rgba(248, 113, 113, 0.18);
  --accent-border: rgba(196, 160, 255, 0.20);
  --green-border: rgba(125, 211, 160, 0.20);
  --blue-border: rgba(125, 174, 211, 0.20);
  --orange-border: rgba(211, 160, 125, 0.20);
  --pink-border: rgba(211, 125, 160, 0.20);
  --yellow-border: rgba(211, 204, 125, 0.20);
}

/* ── 다크모드 토글 버튼 ── */
.theme-btn {
  position: fixed;
  bottom: 1.6rem;
  right: 1.6rem;
  z-index: 900;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 1.5px solid var(--border-bright);
  background: var(--surface);
  color: var(--text-dim);
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: var(--shadow-card);
  transition: border-color .2s, transform .2s, background .2s;
  line-height: 1;
  padding: 0;
}
.theme-btn:hover {
  border-color: var(--accent);
  transform: scale(1.1);
}

/* ── 섹션 교차 배경 (라이트모드) ── */
section:nth-child(even) {
  background: linear-gradient(135deg, rgba(124, 58, 237, 0.03) 0%, rgba(2, 132, 199, 0.03) 100%);
}
section:nth-child(odd) {
  background: linear-gradient(135deg, rgba(234, 88, 12, 0.025) 0%, rgba(180, 83, 9, 0.02) 100%);
}

/* 다크모드에서는 더 은은하게 */
[data-theme="dark"] section:nth-child(even) {
  background: linear-gradient(135deg, rgba(196, 160, 255, 0.03) 0%, rgba(125, 174, 211, 0.03) 100%);
}
[data-theme="dark"] section:nth-child(odd) {
  background: linear-gradient(135deg, rgba(211, 160, 125, 0.025) 0%, rgba(211, 204, 125, 0.02) 100%);
}

/* 섹션 구분선 */
section + section {
  border-top: 1px solid var(--border);
}