/* =========================================================
   GESP C++ L1-L8 复习中枢 — 全局样式
   设计方向：深夜终端 + 纸本笔记
   ========================================================= */

/* ---------- 1. 设计令牌 ---------- */
:root {
  /* 颜色 */
  --bg:           #0E1116;
  --bg-soft:      #161B22;
  --bg-card:      #1A1F27;
  --paper:        #F5E6C8;
  --paper-soft:   rgba(245, 230, 200, 0.78);
  --paper-dim:    rgba(245, 230, 200, 0.55);
  --paper-mute:   rgba(245, 230, 200, 0.32);
  --amber:        #E8A33D;
  --amber-soft:   #F2BC65;
  --amber-dim:    rgba(232, 163, 61, 0.16);
  --amber-glow:   rgba(232, 163, 61, 0.45);
  --code:         #7AE2C7;
  --code-2:       #B8A4FF;
  --code-3:       #FFC78A;
  --err:          #E0524C;
  --ok:           #5EC276;
  --line:         rgba(232, 163, 61, 0.18);
  --line-soft:    rgba(245, 230, 200, 0.08);

  /* 字体 */
  --font-display: "Fraunces", "Source Serif Pro", "Noto Serif SC", Georgia, serif;
  --font-body:    "Inter Tight", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono:    "JetBrains Mono", "Fira Code", "Cascadia Code", Consolas, monospace;

  /* 间距与尺寸 */
  --radius:       10px;
  --radius-sm:    6px;
  --radius-lg:    16px;
  --shadow-card:  0 1px 0 rgba(232, 163, 61, 0.06) inset,
                  0 14px 30px -22px rgba(0, 0, 0, 0.6);
  --maxw:         1240px;
}

/* ---------- 2. 基础重置 ---------- */
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-body);
  font-size: 15.5px;
  line-height: 1.65;
  color: var(--paper);
  background-color: var(--bg);
  background-image:
    radial-gradient(circle at 20% 10%, rgba(232, 163, 61, 0.06) 0%, transparent 40%),
    radial-gradient(circle at 85% 90%, rgba(122, 226, 199, 0.04) 0%, transparent 50%),
    linear-gradient(rgba(245, 230, 200, 0.025) 1px, transparent 1px),
    linear-gradient(90deg, rgba(245, 230, 200, 0.025) 1px, transparent 1px);
  background-size: auto, auto, 32px 32px, 32px 32px;
  background-attachment: fixed;
  min-height: 100vh;
  overflow-x: hidden;
}
a { color: var(--amber-soft); text-decoration: none; transition: color 0.18s ease; }
a:hover { color: var(--amber); }
::selection { background: var(--amber); color: #0E1116; }
img { max-width: 100%; display: block; }
button { font: inherit; color: inherit; cursor: pointer; }

/* ---------- 3. 排版 ---------- */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--paper);
  line-height: 1.2;
}
h1 { font-size: clamp(2.4rem, 5vw, 3.6rem); font-weight: 700; }
h2 { font-size: clamp(1.6rem, 3vw, 2.2rem); }
h3 { font-size: 1.3rem; }
h4 { font-size: 1.05rem; }
p  { color: var(--paper-soft); }
.mono { font-family: var(--font-mono); }
.serif { font-family: var(--font-display); }
.dim { color: var(--paper-dim); }
.mute { color: var(--paper-mute); }
.amber { color: var(--amber); }
mark {
  background: linear-gradient(transparent 60%, var(--amber-dim) 60%);
  color: var(--amber-soft);
  padding: 0 0.1em;
}
code:not(pre code) {
  font-family: var(--font-mono);
  font-size: 0.92em;
  color: var(--code);
  background: rgba(122, 226, 199, 0.08);
  padding: 0.1em 0.45em;
  border-radius: 4px;
  border: 1px solid rgba(122, 226, 199, 0.18);
}

/* ---------- 4. 顶栏导航 ---------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  background: rgba(14, 17, 22, 0.72);
  border-bottom: 1px solid var(--line);
}
.topbar-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 14px 28px;
  display: flex;
  align-items: center;
  gap: 28px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  font-family: var(--font-display);
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--paper);
  letter-spacing: -0.01em;
}
.brand-mark {
  width: 32px; height: 32px;
  border-radius: 8px;
  background: linear-gradient(135deg, var(--amber), #C97B22);
  display: grid; place-items: center;
  font-family: var(--font-mono);
  font-weight: 700;
  color: #0E1116;
  box-shadow: 0 0 0 1px var(--amber-glow), 0 4px 14px -4px var(--amber-glow);
}
.brand small {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.65rem;
  color: var(--paper-mute);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  margin-top: 2px;
}
nav.main {
  display: flex;
  gap: 4px;
  margin-left: auto;
  flex-wrap: wrap;
}
nav.main a {
  color: var(--paper-dim);
  padding: 8px 14px;
  border-radius: var(--radius-sm);
  font-size: 0.92rem;
  font-weight: 500;
  transition: all 0.18s ease;
  position: relative;
}
nav.main a:hover { color: var(--paper); background: rgba(232, 163, 61, 0.06); }
nav.main a.active {
  color: var(--amber);
  background: var(--amber-dim);
}
nav.main a.active::after {
  content: "";
  position: absolute;
  left: 14px; right: 14px;
  bottom: 2px;
  height: 1px;
  background: var(--amber);
}

/* ---------- 5. 容器 ---------- */
.container {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 48px 28px 80px;
}
.container.narrow { max-width: 880px; }

/* ---------- 6. 英雄区 ---------- */
.hero {
  position: relative;
  padding: 64px 0 48px;
  border-bottom: 1px dashed var(--line);
  margin-bottom: 56px;
}
.hero-banner {
  display: block;
  width: 100%;
  height: auto;
  margin: 0 0 36px;
  border-radius: 12px;
  border: 1px solid var(--line);
  box-shadow: 0 14px 40px -16px rgba(0, 0, 0, 0.55),
              0 0 0 1px rgba(232, 163, 61, 0.04);
  background: var(--bg-soft);
}
.hero .eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 0.74rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--amber);
  background: var(--amber-dim);
  padding: 6px 12px;
  border-radius: 100px;
  margin-bottom: 22px;
}
.hero .eyebrow::before {
  content: "";
  width: 6px; height: 6px;
  background: var(--amber);
  border-radius: 50%;
  box-shadow: 0 0 0 4px var(--amber-glow);
}
.hero h1 {
  margin-bottom: 18px;
  max-width: 16ch;
}
.hero h1 em {
  font-style: italic;
  font-weight: 400;
  color: var(--amber-soft);
}
.hero .lede {
  max-width: 60ch;
  font-size: 1.05rem;
  color: var(--paper-dim);
  margin-bottom: 28px;
}
.hero .cta {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
}
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 22px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--line);
  font-weight: 500;
  font-size: 0.95rem;
  background: transparent;
  color: var(--paper);
  transition: all 0.2s ease;
}
.btn:hover { transform: translateY(-1px); border-color: var(--amber); color: var(--amber); }
.btn-primary {
  background: var(--amber);
  color: #0E1116;
  border-color: var(--amber);
  font-weight: 600;
}
.btn-primary:hover { background: var(--amber-soft); color: #0E1116; }
.btn .arrow { transition: transform 0.2s ease; }
.btn:hover .arrow { transform: translateX(3px); }

/* ---------- 7. 统计卡片组 ---------- */
.stat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 14px;
  margin-bottom: 56px;
}
.stat {
  border: 1px solid var(--line);
  background: var(--bg-card);
  padding: 20px 22px;
  border-radius: var(--radius);
  position: relative;
  overflow: hidden;
  transition: all 0.2s ease;
}
.stat:hover { border-color: var(--amber); transform: translateY(-2px); }
.stat::before {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--amber), transparent);
  opacity: 0;
  transition: opacity 0.3s;
}
.stat:hover::before { opacity: 1; }
.stat .label {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--paper-mute);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  margin-bottom: 10px;
}
.stat .value {
  font-family: var(--font-display);
  font-size: 2.1rem;
  font-weight: 600;
  color: var(--paper);
  line-height: 1;
}
.stat .delta {
  font-size: 0.78rem;
  color: var(--amber);
  margin-top: 8px;
  font-family: var(--font-mono);
}

/* ---------- 8. 章节标题 ---------- */
.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 24px;
  padding-bottom: 14px;
  border-bottom: 1px dashed var(--line);
  flex-wrap: wrap;
  gap: 10px;
}
.section-head h2 {
  display: flex; align-items: baseline; gap: 12px;
}
.section-head h2 .num {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: var(--amber);
  font-weight: 400;
}
.section-head .meta {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--paper-mute);
  letter-spacing: 0.1em;
}

/* ---------- 9. 路线图（首页 SVG） ---------- */
.roadmap {
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 36px;
  margin-bottom: 56px;
  position: relative;
  overflow: hidden;
}
.roadmap::before {
  content: "/* knowledge graph */";
  position: absolute;
  top: 12px; right: 18px;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--paper-mute);
  letter-spacing: 0.12em;
}
.roadmap svg {
  width: 100%;
  height: auto;
  display: block;
}
.roadmap .node {
  cursor: pointer;
  transition: transform 0.2s ease;
}
.roadmap .node:hover { transform: scale(1.04); }
.roadmap .node text {
  font-family: var(--font-mono);
  font-size: 13px;
  fill: var(--paper);
  pointer-events: none;
}
.roadmap .node-center text { fill: #0E1116; font-weight: 700; }
.roadmap .node-alg text { fill: #0E1116; }
.roadmap .legend {
  display: flex; gap: 18px;
  flex-wrap: wrap;
  margin-top: 18px;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--paper-dim);
}
.roadmap .legend span { display: inline-flex; align-items: center; gap: 6px; }
.roadmap .legend i { width: 10px; height: 10px; border-radius: 50%; display: inline-block; }

/* ---------- 10. 入口卡片 ---------- */
.entry-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 16px;
  margin-bottom: 56px;
}
.entry {
  display: block;
  padding: 26px 26px 24px;
  border: 1px solid var(--line);
  background: var(--bg-card);
  border-radius: var(--radius);
  position: relative;
  overflow: hidden;
  transition: all 0.22s ease;
  text-decoration: none;
  color: inherit;
}
.entry:hover {
  border-color: var(--amber);
  transform: translateY(-3px);
  background: linear-gradient(180deg, var(--bg-card), rgba(232, 163, 61, 0.04));
}
.entry .tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.16em;
  color: var(--amber);
  margin-bottom: 14px;
}
.entry h3 {
  margin-bottom: 8px;
  font-size: 1.4rem;
}
.entry p {
  font-size: 0.92rem;
  color: var(--paper-dim);
  line-height: 1.55;
  margin-bottom: 16px;
}
.entry .more {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--amber);
  display: inline-flex; align-items: center; gap: 6px;
}
.entry .deco {
  position: absolute;
  right: -10px; bottom: -20px;
  font-family: var(--font-display);
  font-size: 5.5rem;
  font-weight: 700;
  color: var(--amber);
  opacity: 0.04;
  pointer-events: none;
  font-style: italic;
}

/* ---------- 10.5 等级地图（L1-L8） ---------- */
.levels {
  margin-bottom: 56px;
}
.levels-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 14px;
}
.level-card {
  position: relative;
  display: block;
  padding: 22px 20px 20px;
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  text-decoration: none;
  color: inherit;
  transition: transform .25s ease, border-color .25s ease, background .25s ease;
  overflow: hidden;
}
.level-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 3px;
  background: var(--amber);
  opacity: 0.35;
  transition: opacity .25s ease;
}
.level-card:hover {
  transform: translateY(-3px);
  border-color: var(--amber);
  background: linear-gradient(180deg, var(--bg-card), rgba(232, 163, 61, 0.05));
}
.level-card:hover::before { opacity: 1; }
.level-card.is-soon {
  cursor: not-allowed;
  opacity: 0.55;
}
.level-card.is-soon:hover {
  transform: none;
  border-color: var(--line);
  background: var(--bg-card);
}
.level-card.is-live {
  border-color: rgba(232, 163, 61, 0.55);
  background: linear-gradient(180deg, rgba(232, 163, 61, 0.08), var(--bg-card));
}
.level-card.is-live::before { opacity: 1; }
.level-num {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 2.4rem;
  line-height: 1;
  color: var(--amber);
  letter-spacing: -0.02em;
  margin-bottom: 6px;
}
.level-card.is-soon .level-num { color: var(--paper-dim); }
.level-name {
  font-family: 'Inter Tight', sans-serif;
  font-weight: 600;
  font-size: 1rem;
  color: var(--paper);
  margin-bottom: 4px;
}
.level-meta {
  font-size: 0.78rem;
  color: var(--paper-dim);
  line-height: 1.4;
  min-height: 2.2em;
  margin-bottom: 14px;
}
.level-status {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  padding: 3px 8px;
  border-radius: 4px;
  text-transform: uppercase;
}
.status-live {
  background: rgba(94, 194, 118, 0.12);
  color: #5EC276;
  border: 1px solid rgba(94, 194, 118, 0.35);
}
.status-live::before {
  content: '';
  width: 6px; height: 6px;
  border-radius: 50%;
  background: #5EC276;
  box-shadow: 0 0 6px #5EC276;
  animation: levelPulse 1.6s ease-in-out infinite;
}
@keyframes levelPulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.4; transform: scale(0.7); }
}
.status-soon {
  background: rgba(245, 230, 200, 0.06);
  color: var(--paper-dim);
  border: 1px solid var(--line);
}
.status-soon::before {
  content: '';
  width: 5px; height: 5px;
  border-radius: 50%;
  background: var(--paper-dim);
}
.level-card .arrow-go {
  position: absolute;
  top: 18px; right: 16px;
  color: var(--amber);
  font-size: 1.2rem;
  opacity: 0;
  transform: translateX(-4px);
  transition: opacity .25s ease, transform .25s ease;
}
.level-card.is-live:hover .arrow-go {
  opacity: 1;
  transform: translateX(0);
}
@media (max-width: 900px) {
  .levels-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 480px) {
  .levels-grid { grid-template-columns: 1fr; }
  .level-card { padding: 18px 16px; }
}

/* ---------- 10.6 L1-L8 多等级扩展样式 ---------- */
.nav-link.is-active {
  color: var(--level-accent, var(--amber));
  background: rgba(232, 163, 61, 0.08);
}
.nav-link.is-active::after {
  content: "";
  position: absolute;
  left: 14px; right: 14px;
  bottom: 2px;
  height: 1px;
  background: var(--level-accent, var(--amber));
}
.nav-levels {
  margin-left: 6px;
  padding: 6px 12px !important;
  border: 1px dashed rgba(232, 163, 61, 0.45);
  border-radius: 6px !important;
  font-family: var(--font-mono) !important;
  font-size: 0.78rem !important;
  letter-spacing: 0.06em;
  color: var(--paper) !important;
}
.nav-levels:hover {
  background: rgba(232, 163, 61, 0.1) !important;
  border-style: solid;
}

/* 本级考点速览 — chip 列表 */
.topic-chips {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 10px;
  margin-bottom: 48px;
}
.topic-chips li {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: 8px;
  font-size: 0.95rem;
  transition: border-color .2s ease, transform .2s ease;
}
.topic-chips li:hover {
  border-color: var(--level-accent, var(--amber));
  transform: translateX(2px);
}
.topic-chips .dot {
  width: 8px; height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
  box-shadow: 0 0 8px currentColor;
}
.topic-chips small {
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--paper-dim);
  letter-spacing: 0.04em;
  text-align: right;
  max-width: 60%;
}

/* 等级选择器主网格（root index.html） */
.level-selector-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  margin-bottom: 56px;
}
@media (max-width: 1000px) { .level-selector-grid { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 540px)  { .level-selector-grid { grid-template-columns: 1fr; } }

.level-selector-card {
  position: relative;
  display: block;
  padding: 24px 20px 22px;
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: 12px;
  text-decoration: none;
  color: inherit;
  transition: transform .25s ease, border-color .25s ease, background .25s ease;
  overflow: hidden;
}
.level-selector-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 3px;
  background: var(--level-color, var(--amber));
  opacity: 0.6;
}
.level-selector-card:hover {
  transform: translateY(-4px);
  border-color: var(--level-color, var(--amber));
}
.level-selector-card .lvl-num {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 2.4rem;
  line-height: 1;
  color: var(--level-color, var(--amber));
  margin-bottom: 6px;
}
.level-selector-card .lvl-name {
  font-weight: 600;
  font-size: 1.05rem;
  margin-bottom: 4px;
}
.level-selector-card .lvl-en {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--paper-mute);
  margin-bottom: 10px;
}
.level-selector-card .lvl-tagline {
  font-size: 0.86rem;
  color: var(--paper-dim);
  line-height: 1.5;
  margin-bottom: 14px;
  min-height: 2.6em;
}
.level-selector-card .lvl-stats {
  display: flex;
  gap: 12px;
  font-family: var(--font-mono);
  font-size: 0.74rem;
  color: var(--paper-dim);
}
.level-selector-card .lvl-stats b {
  color: var(--level-color, var(--amber));
  font-weight: 700;
  margin-right: 2px;
}
.level-selector-card .lvl-arrow {
  position: absolute;
  right: 16px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.4rem;
  color: var(--paper-mute);
  opacity: 0;
  transition: opacity .2s ease, right .2s ease, color .2s ease;
}
.level-selector-card:hover .lvl-arrow {
  opacity: 1;
  right: 12px;
  color: var(--level-color, var(--amber));
}

/* ---------- 10.7 练习 / 错题进度条 ---------- */
.practice-meta {
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 22px;
  margin-bottom: 28px;
}
.practice-meta .meta-row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding: 4px 0;
  font-size: 0.92rem;
}
.practice-meta .meta-key {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--level-accent, var(--amber));
  letter-spacing: 0.06em;
}
.practice-meta .meta-val {
  color: var(--paper);
  font-weight: 500;
}
.practice-meta .bar {
  height: 6px;
  background: rgba(245, 230, 200, 0.06);
  border-radius: 100px;
  overflow: hidden;
  margin: 8px 0;
}
.practice-meta .bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--level-accent, var(--amber)), var(--amber-soft));
  border-radius: 100px;
  transition: width .3s ease;
}

/* ---------- 10.8 hero 圆圈图标 (L 数字) ---------- */
.hero .lvl-circle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 64px; height: 64px;
  border-radius: 50%;
  background: var(--level-accent, var(--amber));
  color: #0E1116;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.6rem;
  margin-bottom: 14px;
}

/* ---------- 10.9 topic-chips 第 2 级 hover 提升 ---------- */
.topic-chips li small { color: var(--paper-dim); }

/* ---------- 10.10 snippet 搜索框增强 ---------- */
.snippet-search input {
  width: 100%;
  max-width: 460px;
  padding: 10px 16px;
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--paper);
  font-family: var(--font-mono);
  font-size: 0.92rem;
  transition: border-color .2s;
  margin-bottom: 22px;
}
.snippet-search input:focus {
  outline: none;
  border-color: var(--level-accent, var(--amber));
}

/* ---------- 10.11 sub-h (代码题小标题) ---------- */
.sub-h {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--level-accent, var(--amber));
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin: 18px 0 10px;
}

/* ---------- 10.12 review-stats 用 .stat 子元素 ---------- */
.review-stats .stat {
  flex: 1;
  min-width: 160px;
}

/* ---------- 10.13 小按钮 ---------- */
.btn.btn-sm { padding: 6px 12px; font-size: 0.78rem; }

/* ---------- 11. 知识图谱页 ---------- */
.layout-split {
  display: grid;
  grid-template-columns: 260px 1fr;
  gap: 36px;
  align-items: start;
}
@media (max-width: 900px) {
  .layout-split { grid-template-columns: 1fr; }
  .toc { position: static !important; }
}
.toc {
  position: sticky;
  top: 80px;
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 18px 12px;
  max-height: calc(100vh - 100px);
  overflow-y: auto;
}
.toc h4 {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.18em;
  color: var(--paper-mute);
  text-transform: uppercase;
  margin: 12px 0 8px;
  font-weight: 500;
}
.toc h4:first-child { margin-top: 0; }
.toc ul { list-style: none; }
.toc a {
  display: block;
  padding: 6px 10px;
  font-size: 0.88rem;
  color: var(--paper-dim);
  border-left: 2px solid transparent;
  border-radius: 3px;
  transition: all 0.15s ease;
}
.toc a:hover { color: var(--amber); background: var(--amber-dim); border-left-color: var(--amber); }

/* 知识卡片 */
.topic-card {
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px 30px;
  margin-bottom: 22px;
  scroll-margin-top: 80px;
  transition: border-color 0.2s ease;
}
.topic-card:hover { border-color: rgba(232, 163, 61, 0.4); }
.topic-card header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 10px;
  flex-wrap: wrap;
  gap: 8px;
}
.topic-card h2 {
  font-size: 1.55rem;
  display: flex; align-items: baseline; gap: 14px;
}
.topic-card h2 .id {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--amber);
  font-weight: 400;
}
.topic-card .summary {
  color: var(--paper-dim);
  margin-bottom: 18px;
  font-size: 1rem;
  font-style: italic;
}
.topic-card .meta-row {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  margin-bottom: 18px;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--paper-dim);
}
.topic-card .meta-row span {
  display: inline-flex; align-items: center; gap: 6px;
}
.topic-card .meta-row b { color: var(--code); font-weight: 500; }
.topic-card h3 {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--amber);
  margin: 20px 0 10px;
  font-weight: 500;
  border-bottom: 1px dashed var(--line);
  padding-bottom: 6px;
}
.topic-card p { color: var(--paper-soft); margin-bottom: 12px; }
.topic-card ul { padding-left: 20px; color: var(--paper-soft); }
.topic-card ul li { margin-bottom: 6px; }
.topic-card ul li::marker { color: var(--amber); }
.topic-card .concept code { font-size: 0.88em; }

/* ---------- 12. 代码块 ---------- */
.code-block {
  position: relative;
  background: #0A0D12;
  border: 1px solid var(--line-soft);
  border-radius: var(--radius-sm);
  padding: 18px 20px;
  margin: 14px 0;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  line-height: 1.6;
  color: var(--paper);
}
.code-block::before {
  content: attr(data-lang);
  position: absolute;
  top: 8px; left: 14px;
  font-size: 0.65rem;
  letter-spacing: 0.16em;
  color: var(--amber);
  text-transform: uppercase;
  opacity: 0.5;
}
.code-block pre { margin: 0; }
.code-block pre code { background: none !important; border: none !important; padding: 0 !important; color: inherit; }
.code-block .copy {
  position: absolute;
  top: 8px; right: 10px;
  background: transparent;
  border: 1px solid var(--line);
  color: var(--paper-dim);
  padding: 4px 10px;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  border-radius: 4px;
  transition: all 0.15s ease;
}
.code-block .copy:hover { color: var(--amber); border-color: var(--amber); }
.code-block .copy.ok { color: var(--ok); border-color: var(--ok); }

/* 自实现语法高亮 */
.tok-kw   { color: #FF9D6B; }
.tok-ty   { color: #FFC78A; }
.tok-fn   { color: #9DCCFF; }
.tok-num  { color: #E0A6FF; }
.tok-str  { color: #7AE2C7; }
.tok-com  { color: #5C6A7A; font-style: italic; }
.tok-pp   { color: #FFB1B1; }
.tok-op   { color: var(--paper-soft); }

/* ---------- 13. 搜索 / 过滤 ---------- */
.toolbar {
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
  margin-bottom: 24px;
  padding: 14px 18px;
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}
.search {
  flex: 1;
  min-width: 240px;
  position: relative;
}
.search input {
  width: 100%;
  background: var(--bg);
  border: 1px solid var(--line);
  color: var(--paper);
  padding: 10px 14px 10px 38px;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.9rem;
  outline: none;
  transition: border-color 0.15s ease;
}
.search input:focus { border-color: var(--amber); }
.search::before {
  content: ">";
  position: absolute;
  left: 14px; top: 50%;
  transform: translateY(-50%);
  font-family: var(--font-mono);
  color: var(--amber);
  font-size: 0.95rem;
}
.filter-chips {
  display: flex; gap: 6px; flex-wrap: wrap;
}
.chip {
  padding: 6px 12px;
  border: 1px solid var(--line);
  background: transparent;
  color: var(--paper-dim);
  font-family: var(--font-mono);
  font-size: 0.78rem;
  border-radius: 100px;
  transition: all 0.15s ease;
}
.chip:hover { color: var(--paper); }
.chip.active { background: var(--amber); color: #0E1116; border-color: var(--amber); }

/* ---------- 14. 题目卡 ---------- */
.q-card {
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px;
  margin-bottom: 22px;
}
.q-card .q-head {
  display: flex; justify-content: space-between; align-items: baseline;
  margin-bottom: 16px;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--paper-mute);
  letter-spacing: 0.12em;
}
.q-card .q-head .qid { color: var(--amber); }
.q-card .q-head .qtopic { text-transform: uppercase; }
.q-card .q-stem {
  font-size: 1.05rem;
  color: var(--paper);
  margin-bottom: 18px;
  line-height: 1.6;
}
.q-opts { list-style: none; }
.q-opts li {
  margin-bottom: 10px;
}
.q-opts label {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 12px 16px;
  border: 1px solid var(--line);
  background: rgba(245, 230, 200, 0.02);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.15s ease;
}
.q-opts label:hover { background: var(--amber-dim); border-color: var(--amber); }
.q-opts input[type="radio"] {
  margin-top: 4px;
  accent-color: var(--amber);
  cursor: pointer;
}
.q-opts .opt-text { flex: 1; }
.q-card .q-actions { margin-top: 16px; display: flex; gap: 10px; align-items: center; }
.q-card .feedback {
  margin-top: 16px;
  padding: 14px 18px;
  border-radius: var(--radius-sm);
  font-size: 0.92rem;
  line-height: 1.6;
  display: none;
}
.q-card.correct .feedback { display: block; background: rgba(94, 194, 118, 0.1); border-left: 3px solid var(--ok); color: var(--ok); }
.q-card.wrong .feedback { display: block; background: rgba(224, 82, 76, 0.1); border-left: 3px solid var(--err); color: var(--err); }
.q-card.correct .feedback b { color: var(--ok); }
.q-card.wrong .feedback b { color: var(--err); }

/* 代码题 */
.cq-card {
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px;
  margin-bottom: 22px;
}
.cq-card .cq-head {
  display: flex; justify-content: space-between; align-items: baseline;
  margin-bottom: 14px;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--paper-mute);
  letter-spacing: 0.12em;
}
.cq-card h3 { font-size: 1.35rem; margin-bottom: 10px; }
.cq-card .desc { color: var(--paper-soft); margin-bottom: 14px; }
.cq-card .hint {
  background: var(--amber-dim);
  border-left: 3px solid var(--amber);
  padding: 10px 14px;
  border-radius: 4px;
  font-size: 0.9rem;
  color: var(--amber-soft);
  margin-bottom: 14px;
}
.cq-card .complexity {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--code);
  margin-top: 12px;
}

/* ---------- 15. 错题本 ---------- */
.review-empty {
  text-align: center;
  padding: 80px 20px;
  color: var(--paper-dim);
  font-family: var(--font-mono);
}
.review-empty .icon {
  font-size: 3rem;
  color: var(--amber);
  opacity: 0.4;
  margin-bottom: 16px;
}
.review-stats {
  display: flex; gap: 16px; margin-bottom: 24px; flex-wrap: wrap;
}
.review-stat {
  flex: 1;
  min-width: 160px;
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 20px;
}
.review-stat .lbl { font-family: var(--font-mono); font-size: 0.72rem; color: var(--paper-mute); letter-spacing: 0.16em; text-transform: uppercase; margin-bottom: 6px; }
.review-stat .val { font-family: var(--font-display); font-size: 1.8rem; color: var(--paper); }
.review-stat.ok .val { color: var(--ok); }
.review-stat.err .val { color: var(--err); }

/* ---------- 16. 进度条 ---------- */
.progress {
  height: 6px;
  background: rgba(245, 230, 200, 0.06);
  border-radius: 100px;
  overflow: hidden;
  margin-top: 10px;
}
.progress > span {
  display: block;
  height: 100%;
  background: linear-gradient(90deg, var(--amber), var(--amber-soft));
  border-radius: 100px;
  transition: width 0.4s ease;
}

/* ---------- 17. 关于页 ---------- */
.about-grid {
  display: grid;
  grid-template-columns: 2fr 1fr;
  gap: 28px;
}
@media (max-width: 800px) { .about-grid { grid-template-columns: 1fr; } }
.about-grid .panel {
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px 28px;
}
.about-grid h3 {
  font-size: 1.15rem;
  margin-bottom: 14px;
  display: flex; align-items: baseline; gap: 10px;
}
.about-grid h3::before {
  content: "▍";
  color: var(--amber);
  font-family: var(--font-mono);
}
.about-grid ul { padding-left: 20px; }
.about-grid li { margin-bottom: 8px; color: var(--paper-soft); }
.about-grid li::marker { color: var(--amber); }
.about-grid .info-row {
  display: flex; justify-content: space-between;
  padding: 8px 0;
  border-bottom: 1px dashed var(--line);
  font-size: 0.92rem;
}
.about-grid .info-row:last-child { border-bottom: none; }
.about-grid .info-row span:first-child { color: var(--paper-mute); }
.about-grid .info-row span:last-child { color: var(--paper); font-family: var(--font-mono); }

/* ---------- 18. 页脚 ---------- */
footer.site {
  border-top: 1px solid var(--line);
  margin-top: 80px;
  padding: 28px;
  text-align: center;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--paper-mute);
  letter-spacing: 0.1em;
}
footer.site .ascii {
  display: block;
  white-space: pre;
  color: var(--amber);
  opacity: 0.35;
  font-size: 0.7rem;
  line-height: 1.2;
  margin-bottom: 12px;
  user-select: none;
}

/* ---------- 19. 工具类 ---------- */
.row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.between { justify-content: space-between; }
.mt-1 { margin-top: 8px; } .mt-2 { margin-top: 16px; } .mt-3 { margin-top: 24px; } .mt-4 { margin-top: 32px; }
.mb-1 { margin-bottom: 8px; } .mb-2 { margin-bottom: 16px; } .mb-3 { margin-bottom: 24px; }
.tag-pill {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 100px;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  border: 1px solid var(--line);
  color: var(--paper-dim);
}
.tag-pill.amber { color: var(--amber); border-color: var(--amber); }
.tag-pill.code  { color: var(--code); border-color: rgba(122, 226, 199, 0.4); }

/* ---------- 20. 入场动画 ---------- */
@keyframes rise {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}
.rise { animation: rise 0.5s ease both; }
.rise:nth-child(1) { animation-delay: 0.04s; }
.rise:nth-child(2) { animation-delay: 0.10s; }
.rise:nth-child(3) { animation-delay: 0.16s; }
.rise:nth-child(4) { animation-delay: 0.22s; }
.rise:nth-child(5) { animation-delay: 0.28s; }
.rise:nth-child(6) { animation-delay: 0.34s; }

@keyframes blink { 50% { opacity: 0.2; } }
.cursor { animation: blink 1.1s steps(2) infinite; color: var(--amber); }

/* ---------- 21. 滚动条 ---------- */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: rgba(232, 163, 61, 0.25); border-radius: 100px; }
::-webkit-scrollbar-thumb:hover { background: var(--amber); }

/* ---------- 22. 移动端 ---------- */
@media (max-width: 640px) {
  .topbar-inner { padding: 12px 16px; gap: 12px; flex-wrap: wrap; }
  nav.main { width: 100%; margin-left: 0; }
  nav.main a { padding: 6px 10px; font-size: 0.85rem; }
  .container { padding: 32px 16px 60px; }
  .hero { padding: 36px 0 28px; }
  .roadmap { padding: 22px 16px; }
  .topic-card, .q-card, .cq-card { padding: 22px 18px; }
  .stat-grid { grid-template-columns: 1fr 1fr; }
}