/* ============================================================
   《动手学大模型》学习站 v3 — 科幻驾驶舱 HUD 主题
   风格: 深空背景 · 青色辉光 · 玻璃面板 · 切角舱门 · 扫描线
   ============================================================ */
:root {
  /* 驾驶舱色板 */
  --bg0: #03060d;              /* 深空 */
  --bg1: #070d1a;
  --panel: rgba(12, 20, 36, 0.72);
  --panel-2: rgba(18, 30, 52, 0.85);
  --panel-3: #0c1526;
  --hud: #3ee6ff;              /* 主 HUD 青 */
  --hud-dim: rgba(62, 230, 255, 0.45);
  --hud-faint: rgba(62, 230, 255, 0.14);
  --amber: #ffc45e;            /* 琥珀高亮 */
  --magenta: #ff5c9d;
  --ok: #3dffa0;
  --alert: #ff4d5e;
  --txt: #cfe3f7;
  --txt-2: #9fb6d4;
  --txt-dim: #5f789c;
  --line: rgba(94, 200, 255, 0.16);
  --line-strong: rgba(94, 200, 255, 0.4);
  --glow: 0 0 18px rgba(62, 230, 255, 0.25);
  --glow-soft: 0 0 10px rgba(62, 230, 255, 0.14);
  --serif: "Songti SC", "Noto Serif SC", "STSong", serif;
  --sans: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --mono: "SF Mono", "JetBrains Mono", Menlo, Consolas, "Courier New", monospace;
  --radius-s: 6px;
  --radius-m: 10px;
  --radius-l: 14px;
  --clip-corner: polygon(0 0, calc(100% - 18px) 0, 100% 18px, 100% 100%, 18px 100%, 0 calc(100% - 18px));
}
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; scroll-padding-top: 92px; }
body {
  background:
    radial-gradient(1100px 520px at 78% -12%, rgba(46, 90, 190, 0.22), transparent 62%),
    radial-gradient(900px 500px at 8% 4%, rgba(120, 50, 180, 0.16), transparent 55%),
    radial-gradient(700px 700px at 50% 118%, rgba(20, 120, 160, 0.14), transparent 60%),
    var(--bg0);
  color: var(--txt);
  font: 16px/1.8 var(--sans);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  min-height: 100vh;
}
a { color: var(--hud); text-decoration: none; }
a:hover { text-shadow: 0 0 12px var(--hud-dim); }
::selection { background: rgba(62, 230, 255, 0.35); color: #fff; }

/* 背景星点层 */
body::before {
  content: ""; position: fixed; inset: 0; z-index: -2; pointer-events: none;
  background-image:
    radial-gradient(1px 1px at 8% 22%, rgba(255,255,255,.7), transparent 100%),
    radial-gradient(1px 1px at 22% 71%, rgba(255,255,255,.5), transparent 100%),
    radial-gradient(1.4px 1.4px at 35% 12%, rgba(200,235,255,.8), transparent 100%),
    radial-gradient(1px 1px at 46% 45%, rgba(255,255,255,.4), transparent 100%),
    radial-gradient(1.6px 1.6px at 58% 8%, rgba(170,230,255,.75), transparent 100%),
    radial-gradient(1px 1px at 63% 33%, rgba(255,255,255,.5), transparent 100%),
    radial-gradient(1.2px 1.2px at 71% 78%, rgba(190,240,255,.6), transparent 100%),
    radial-gradient(1px 1px at 80% 26%, rgba(255,255,255,.35), transparent 100%),
    radial-gradient(1.5px 1.5px at 88% 62%, rgba(200,235,255,.6), transparent 100%),
    radial-gradient(1px 1px at 92% 88%, rgba(255,255,255,.4), transparent 100%),
    radial-gradient(1px 1px at 15% 88%, rgba(255,255,255,.5), transparent 100%),
    radial-gradient(1.3px 1.3px at 42% 92%, rgba(170,230,255,.55), transparent 100%),
    radial-gradient(1px 1px at 96% 10%, rgba(255,255,255,.5), transparent 100%),
    radial-gradient(1px 1px at 3% 50%, rgba(255,255,255,.3), transparent 100%);
}
/* 极淡扫描网格 */
body::after {
  content: ""; position: fixed; inset: 0; z-index: -1; pointer-events: none; opacity: 0.5;
  background-image:
    linear-gradient(rgba(62, 230, 255, 0.028) 1px, transparent 1px),
    linear-gradient(90deg, rgba(62, 230, 255, 0.028) 1px, transparent 1px);
  background-size: 44px 44px;
  mask-image: radial-gradient(ellipse at 50% 0%, #000 0%, transparent 72%);
  -webkit-mask-image: radial-gradient(ellipse at 50% 0%, #000 0%, transparent 72%);
}

/* ---------- 顶部导航（驾驶舱横梁） ---------- */
.topbar {
  position: sticky; top: 0; z-index: 60;
  background: rgba(4, 9, 18, 0.72);
  backdrop-filter: blur(16px) saturate(1.4);
  border-bottom: 1px solid var(--line);
  box-shadow: 0 1px 0 rgba(62, 230, 255, 0.1) inset;
}
.topbar-inner { max-width: var(--wrap, 1160px); margin: 0 auto; padding: 0 24px; height: 64px;
  display: flex; align-items: center; gap: 22px; }
.brand { display: flex; align-items: center; gap: 11px; font-weight: 700; letter-spacing: 1.5px; font-size: 14px;
  color: var(--txt); text-transform: uppercase; white-space: nowrap; }
.brand:hover { text-decoration: none; text-shadow: none; }
.brand-mark { width: 34px; height: 34px; border-radius: 8px; display: grid; place-items: center;
  background: linear-gradient(135deg, rgba(62,230,255,.16), rgba(255,92,157,.12));
  border: 1px solid var(--hud-dim); color: var(--hud); font-size: 16px;
  box-shadow: var(--glow-soft); position: relative; overflow: hidden; }
.brand-mark::after { content: ""; position: absolute; inset: 0;
  background: linear-gradient(115deg, transparent 40%, rgba(62,230,255,.28) 50%, transparent 60%);
  animation: sheen 5s linear infinite; }
@keyframes sheen { 0% { transform: translateX(-110%); } 60%,100% { transform: translateX(110%); } }
.brand b { color: var(--hud); font-weight: 700; }
.chapter-nav { margin-left: auto; display: flex; align-items: center; gap: 3px; overflow-x: auto; scrollbar-width: none; }
.chapter-nav::-webkit-scrollbar { display: none; }
.chapter-nav a { color: var(--txt-dim); font-family: var(--mono); font-size: 12.5px; padding: 7px 11px;
  border-radius: var(--radius-s); letter-spacing: 0.4px; transition: color .15s, background .15s, box-shadow .15s;
  border: 1px solid transparent; }
.chapter-nav a:hover { color: var(--hud); background: rgba(62,230,255,.07); text-decoration: none; }
.chapter-nav a.active { color: var(--bg0); background: var(--hud); font-weight: 700;
  box-shadow: 0 0 14px rgba(62,230,255,.55); }
.chapter-nav a.nav-home { border-color: var(--line); }
.nav-toggle { display: none; margin-left: auto; width: 40px; height: 40px; border: 1px solid var(--line);
  background: var(--panel); border-radius: var(--radius-s); font-size: 18px; cursor: pointer; color: var(--hud); }
@media (max-width: 900px) {
  .chapter-nav { display: none; position: fixed; inset: 64px 0 auto 0; background: rgba(6,12,24,.97);
    flex-direction: column; align-items: stretch; padding: 12px 18px; backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--line); max-height: 72vh; overflow-y: auto; }
  .chapter-nav.open { display: flex; }
  .nav-toggle { display: grid; place-items: center; }
}

/* ---------- 阅读进度条（能量轨） ---------- */
.read-progress { position: fixed; top: 0; left: 0; height: 2px; width: 100%; z-index: 70;
  background: rgba(62,230,255,.12); }
.read-progress i { display: block; height: 100%; width: 0; background: linear-gradient(90deg, var(--hud), var(--amber));
  box-shadow: 0 0 12px rgba(62,230,255,.9); }

/* ---------- Hero（舰桥视窗） ---------- */
.hero { position: relative; overflow: hidden; border-bottom: 1px solid var(--line);
  background:
    radial-gradient(820px 420px at 70% 0%, rgba(42, 110, 220, 0.28), transparent 60%),
    radial-gradient(600px 360px at 15% 15%, rgba(130, 60, 210, 0.18), transparent 55%); }
/* 扫描光束 */
.hero::before { content: ""; position: absolute; left: 0; right: 0; height: 2px; z-index: 1; pointer-events: none;
  background: linear-gradient(90deg, transparent, rgba(62,230,255,.8), transparent);
  filter: blur(0.4px); animation: scanline 7s linear infinite; opacity: .7; }
@keyframes scanline { 0% { top: 4%; } 50% { top: 96%; } 100% { top: 4%; } }
/* 网格地平线 */
.hero::after { content: ""; position: absolute; inset: 0; pointer-events: none; opacity: .5;
  background:
    linear-gradient(rgba(62,230,255,.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(62,230,255,.05) 1px, transparent 1px);
  background-size: 52px 52px;
  mask-image: radial-gradient(ellipse at 50% 120%, #000 20%, transparent 72%);
  -webkit-mask-image: radial-gradient(ellipse at 50% 120%, #000 20%, transparent 72%); }
.hero-inner { position: relative; max-width: var(--wrap, 1160px); margin: 0 auto; padding: 78px 24px 66px; }
.hero-badge { display: inline-flex; align-items: center; gap: 9px; font: 600 11px/1 var(--mono);
  letter-spacing: 0.24em; text-transform: uppercase; color: var(--hud);
  background: rgba(62,230,255,.07); border: 1px solid var(--hud-dim);
  padding: 7px 14px; margin-bottom: 24px; position: relative; clip-path: var(--clip-corner); }
.hero-badge::before { content: "◈"; margin-right: 2px; color: var(--amber); }
.hero h1 { font-size: clamp(36px, 5.6vw, 54px); line-height: 1.16; letter-spacing: 2px; font-weight: 800;
  color: #e8f4ff; text-transform: uppercase; text-wrap: balance; margin-bottom: 14px;
  font-family: var(--sans); text-shadow: 0 0 26px rgba(62,230,255,.28), 0 2px 0 rgba(0,0,0,.4); }
.hero h1 em { font-style: normal; color: var(--hud);
  text-shadow: 0 0 34px rgba(62,230,255,.65); }
.hero-sub { max-width: 60ch; color: var(--txt-2); font-size: 16px; line-height: 1.9;
  letter-spacing: .4px; margin-bottom: 30px; }
.hero-sub b { color: var(--amber); font-weight: 600; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 14px; }
.btn { position: relative; display: inline-flex; align-items: center; gap: 9px;
  font: 700 13.5px/1 var(--mono); letter-spacing: .12em; text-transform: uppercase;
  padding: 13px 24px; cursor: pointer; border: 1px solid var(--line-strong);
  clip-path: var(--clip-corner); transition: transform .12s ease, box-shadow .22s, background .2s, color .2s; }
.btn:active { transform: scale(0.96); }
.btn-primary { background: linear-gradient(115deg, rgba(62,230,255,.22), rgba(62,230,255,.08)); color: var(--hud);
  box-shadow: var(--glow), inset 0 0 0 1px rgba(62,230,255,.2); }
.btn-primary:hover { background: var(--hud); color: #03121c; box-shadow: 0 0 30px rgba(62,230,255,.75);
  text-decoration: none; }
.btn-ghost { background: rgba(13, 24, 44, .6); color: var(--txt-2); }
.btn-ghost:hover { color: var(--hud); border-color: var(--hud); box-shadow: var(--glow-soft); text-decoration: none; }

/* ---------- 进度总览（状态面板） ---------- */
.summary { max-width: var(--wrap, 1160px); margin: -24px auto 0; padding: 0 24px; position: relative; z-index: 5; }
.summary-card { background: linear-gradient(160deg, rgba(14,24,44,.9), rgba(8,14,28,.9));
  border: 1px solid var(--line); clip-path: var(--clip-corner); padding: 22px 28px;
  display: grid; grid-template-columns: auto 1fr; gap: 22px 28px; align-items: center;
  box-shadow: 0 18px 50px rgba(0,0,0,.5), var(--glow-soft); }
@media (max-width: 720px) { .summary-card { grid-template-columns: 1fr; } }
.progress-ring { position: relative; width: 82px; height: 82px; }
.progress-ring svg { transform: rotate(-90deg); }
.progress-ring .track { stroke: rgba(94,200,255,.14); }
.progress-ring .bar { stroke: var(--hud); stroke-linecap: round; filter: drop-shadow(0 0 5px var(--hud));
  transition: stroke-dashoffset 0.8s cubic-bezier(0.2,0,0,1); }
.progress-ring b { position: absolute; inset: 0; display: grid; place-items: center;
  font: 700 18px var(--mono); color: var(--txt); }
.progress-ring b i { font-style: normal; font-size: 10px; color: var(--txt-dim); display: block; margin-left: 2px; }
.summary-meta h2 { font: 700 13px/1 var(--mono); letter-spacing: .3em; text-transform: uppercase;
  color: var(--hud); margin-bottom: 8px; }
.summary-meta h2::before { content: "▸ "; color: var(--amber); }
.summary-meta p { color: var(--txt-2); font-size: 14px; }
.summary-meta .stat-done { color: var(--hud); font-weight: 700; }
.summary-meta .stats { display: flex; flex-wrap: wrap; gap: 8px 22px; margin-top: 11px;
  font: 500 12.5px var(--mono); color: var(--txt-dim); letter-spacing: .05em; }
.summary-meta .stats b { color: var(--amber); font-weight: 700; }

/* ---------- 容器 ---------- */
.wrap { max-width: var(--wrap, 1160px); margin: 0 auto; padding: 0 24px; }
.section { margin-top: 58px; }
.sec-head { display: flex; align-items: center; gap: 14px; margin-bottom: 22px;
  border-bottom: 1px solid var(--line); padding-bottom: 12px; }
.sec-head h2 { font: 700 19px/1 var(--sans); letter-spacing: 3px; text-transform: uppercase;
  color: var(--txt); }
.sec-head h2::before { content: "◆ "; color: var(--hud); font-size: 13px; }
.sec-head .hint { color: var(--txt-dim); font-size: 13px; letter-spacing: .4px; margin-left: auto;
  font-family: var(--mono); }

/* ---------- 章节网格（机舱面板） ---------- */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 18px; }
.ch-card { position: relative; display: block; color: var(--txt);
  background: linear-gradient(165deg, rgba(16,28,50,.85), rgba(9,15,30,.9));
  border: 1px solid var(--line); clip-path: var(--clip-corner);
  padding: 24px 22px 18px; overflow: hidden;
  transition: transform .2s ease, box-shadow .25s ease, border-color .2s; }
.ch-card::before { content: ""; position: absolute; top: 0; left: 0; width: 100%; height: 2px;
  background: linear-gradient(90deg, transparent, var(--hud), transparent); opacity: 0;
  transition: opacity .3s; }
.ch-card:hover { transform: translateY(-4px); border-color: var(--hud-dim);
  box-shadow: var(--glow); text-decoration: none; }
.ch-card:hover::before { opacity: .9; }
.ch-card.done { border-color: rgba(61,255,160,.35);
  background: linear-gradient(165deg, rgba(14,38,34,.85), rgba(8,18,22,.9)); }
.ch-card-top { display: flex; align-items: flex-start; justify-content: space-between; }
.ch-no { font: 700 11px/1 var(--mono); letter-spacing: .26em; color: var(--hud); }
.ch-no::before { content: "SYS·"; color: var(--txt-dim); }
.ch-card.done .ch-no::before { content: "COMPLETE·"; color: var(--ok); }
.ch-done-badge { font: 600 10.5px/1 var(--mono); letter-spacing: .1em; color: var(--ok);
  background: rgba(61,255,160,.1); border: 1px solid rgba(61,255,160,.35);
  padding: 4px 9px; display: none; }
.ch-card.done .ch-done-badge { display: inline-block; }
.ch-card h3 { font-size: 20px; line-height: 1.4; font-weight: 700; letter-spacing: .6px;
  margin: 12px 0 8px; color: #e8f3ff; }
.ch-card.done h3 { color: var(--ok); }
.ch-card .sub { color: var(--txt-dim); font-size: 13.5px; line-height: 1.75;
  min-height: 46px; margin-bottom: 16px; }
.ch-tags { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 16px; }
.ch-tags span { font: 500 10.5px/1 var(--mono); letter-spacing: .08em; color: var(--txt-2);
  background: rgba(62,230,255,.05); border: 1px solid var(--line); padding: 4px 9px; }
.ch-foot { display: flex; align-items: center; justify-content: space-between;
  border-top: 1px solid var(--line); padding-top: 14px; }
.ch-go { font: 700 12.5px/1 var(--mono); letter-spacing: .14em; color: var(--hud); }
.ch-go .arr { transition: transform .2s ease; display: inline-block; }
.ch-card:hover .ch-go .arr { transform: translateX(5px); }
.ch-reading { font: 500 11px var(--mono); color: var(--txt-dim); }

/* ---------- 章节正文页 ---------- */
.layout { max-width: var(--wrap, 1160px); margin: 0 auto; padding: 0 24px;
  display: grid; grid-template-columns: 250px minmax(0, 1fr); gap: 54px; }
@media (max-width: 960px) { .layout { grid-template-columns: 1fr; gap: 20px; } }
.toc { position: sticky; top: 86px; align-self: start; max-height: calc(100vh - 112px);
  overflow-y: auto; display: block; }
@media (max-width: 960px) { .toc { position: static; max-height: none; } }
.toc-title { font: 700 11px/1 var(--mono); letter-spacing: .3em; text-transform: uppercase;
  color: var(--hud-dim); margin-bottom: 13px; padding-bottom: 9px; border-bottom: 1px solid var(--line); }
.toc-title::before { content: "◤ "; }
.toc a { display: block; font-size: 13px; color: var(--txt-dim); padding: 5px 0 5px 13px;
  border-left: 2px solid transparent; transition: color .15s, border-color .15s, background .15s; }
.toc a:hover { color: var(--txt); text-decoration: none; }
.toc a.toc-h3 { padding-left: 26px; font-size: 12px; }
.toc a.toc-h4 { padding-left: 39px; font-size: 11.5px; opacity: .8; }
.toc a.active { color: var(--hud); border-left-color: var(--hud); background: rgba(62,230,255,.05);
  text-shadow: 0 0 12px var(--hud-dim); }
.article { min-width: 0; max-width: var(--measure, 68ch); }
.article-head { padding: 36px 0 22px; border-bottom: 1px solid var(--line); margin-bottom: 30px;
  position: relative; }
.article-head::before { content: ""; position: absolute; bottom: -1px; left: 0; height: 1px; width: 180px;
  background: linear-gradient(90deg, var(--hud), transparent); }
.crumb { font: 500 12px var(--mono); color: var(--txt-dim); letter-spacing: .12em;
  margin-bottom: 18px; text-transform: uppercase; }
.crumb a { color: var(--hud); }
.article-head h1 { font-size: clamp(26px, 3.6vw, 36px); font-weight: 800; letter-spacing: 1px;
  line-height: 1.28; margin-bottom: 10px; color: #e9f4ff; text-wrap: balance;
  text-shadow: 0 0 22px rgba(62,230,255,.15); }
.article-head h1 .no { color: var(--hud); font-family: var(--mono); margin-right: 10px; }
.article-head .sub { color: var(--txt-2); font-size: 15px; text-wrap: pretty; }
.article-head .meta { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 16px; }
.chip { font: 600 10.5px/1 var(--mono); letter-spacing: .14em; text-transform: uppercase;
  padding: 5px 12px; color: var(--txt-2); background: rgba(62,230,255,.06);
  border: 1px solid var(--line); }
.chip.accent { color: var(--hud); border-color: var(--hud-dim); box-shadow: var(--glow-soft); }
.chip a { color: inherit; }

/* 正文 */
.prose { color: var(--txt-2); font-size: 16px; line-height: 1.85; }
.prose > p { margin: 1.05em 0; }
.prose h2, .prose h3, .prose h4 { color: #dfeeff; font-weight: 700; line-height: 1.4; scroll-margin-top: 96px; }
.prose h2 { font-size: 23px; margin: 2.3em 0 0.7em; padding: 10px 0 12px 18px;
  border-left: 3px solid var(--hud); background: linear-gradient(90deg, rgba(62,230,255,.07), transparent 70%);
  letter-spacing: .4px; text-wrap: balance; }
.prose h2::before { content: "◆"; font-family: var(--mono); color: var(--hud); font-size: 12px;
  margin-right: 12px; vertical-align: 2px; text-shadow: 0 0 8px var(--hud); }
.prose h3 { font-size: 18px; margin: 1.8em 0 0.5em; color: var(--hud); letter-spacing: .3px; }
.prose h3::before { content: "▸ "; font-size: 14px; }
.prose h4 { font-size: 16px; margin: 1.4em 0 0.45em; }
.prose ul, .prose ol { padding-left: 1.5em; margin: 0.8em 0; }
.prose li { margin: 0.4em 0; }
.prose li::marker { color: var(--hud); }
.prose blockquote { position: relative; border-left: 2px solid var(--amber);
  background: rgba(255,196,94,.05); padding: 0.9em 1.3em 0.9em 1.6em; margin: 1.3em 0;
  color: var(--txt-2); font-size: 14.5px; }
.prose blockquote::before { content: "⚠"; position: absolute; left: 10px; top: 14px; color: var(--amber); font-size: 12px; }
.prose code { font-family: var(--mono); font-size: 0.86em; color: var(--amber);
  background: rgba(255,196,94,.09); padding: 0.12em 0.42em; border-radius: 4px; }
.prose a { text-decoration: underline; text-decoration-color: var(--hud-dim); text-underline-offset: 3px; }
.prose a:hover { text-decoration-color: var(--hud); }
.prose img { border-radius: var(--radius-m);
  box-shadow: 0 14px 40px rgba(0,0,0,.5), var(--glow-soft),
  inset 0 0 0 1px rgba(62,230,255,.1);
  outline: 1px solid rgba(120,200,255,.14); margin: 1.4em auto; display: block; }
.prose .md-img { text-align: center; margin: 1.2em 0; }
.prose table { width: 100%; border-collapse: separate; border-spacing: 0; margin: 1.3em 0;
  font-size: 13.5px; border: 1px solid var(--line); }
.prose thead th { background: rgba(62,230,255,.08); color: var(--hud); font-weight: 700;
  text-align: left; padding: 10px 14px; border-bottom: 1px solid var(--line);
  font-family: var(--mono); font-size: 12px; letter-spacing: .06em; }
.prose tbody td { padding: 9px 14px; border-bottom: 1px solid rgba(94,200,255,.07); vertical-align: top; }
.prose tbody tr:last-child td { border-bottom: none; }
.prose tbody tr:nth-child(even) td { background: rgba(62,230,255,.02); }
.prose tbody tr:hover td { background: rgba(62,230,255,.05); }
.prose hr { border: none; height: 1px; margin: 2.4em 0;
  background: linear-gradient(90deg, transparent, var(--hud-dim), transparent); }

/* 代码块（全息终端） */
.code-block { position: relative; margin: 1.5em 0; border-radius: var(--radius-m);
  background: linear-gradient(180deg, #0a101e, #060b16);
  border: 1px solid var(--line); overflow: hidden;
  box-shadow: 0 10px 34px rgba(0,0,0,.45), inset 0 0 24px rgba(62,230,255,.03); }
.code-block::before { content: ""; position: absolute; top: 0; left: 0; right: 0; height: 1px;
  background: linear-gradient(90deg, transparent, var(--hud-dim), transparent); }
.code-block .code-head { display: flex; align-items: center; justify-content: space-between;
  padding: 8px 14px; background: rgba(62,230,255,.04);
  border-bottom: 1px solid rgba(94,200,255,.08); }
.code-block .code-lang { font: 700 10px/1 var(--mono); letter-spacing: .22em; text-transform: uppercase;
  color: var(--hud-dim); }
.code-lang::before { content: "❯ "; }
.copy-btn { font: 600 11px/1 var(--mono); letter-spacing: .06em; color: var(--hud);
  background: rgba(62,230,255,.08); border: 1px solid var(--hud-dim);
  padding: 5px 12px; cursor: pointer; transition: background .15s, color .15s, transform .12s; }
.copy-btn:hover { background: rgba(62,230,255,.2); color: #fff; }
.copy-btn:active { transform: scale(0.96); }
.copy-btn.copied { background: rgba(61,255,160,.2); color: var(--ok); border-color: rgba(61,255,160,.4); }
.code-block pre { padding: 16px 18px; overflow-x: auto; }
.code-block code { display: block; font-family: var(--mono); font-size: 13px; line-height: 1.7;
  color: #b8d8f0; background: none !important; padding: 0 !important; }

/* 章末 */
.article-end { margin-top: 3.4em; }
.mark-done { display: flex; align-items: center; justify-content: space-between; gap: 14px;
  background: linear-gradient(160deg, rgba(14,24,44,.85), rgba(8,14,28,.9));
  border: 1px solid var(--line); padding: 20px 24px; flex-wrap: wrap;
  clip-path: var(--clip-corner); box-shadow: var(--glow-soft); }
.mark-done .md-text b { display: block; font: 700 14px/1.4 var(--sans); letter-spacing: 1px; color: var(--txt); }
.mark-done .md-text span { font-size: 13px; color: var(--txt-dim); }
.mark-done.done-state { border-color: rgba(61,255,160,.35); }
.mark-done.done-state .md-text b { color: var(--ok); }
.pager { display: flex; gap: 14px; margin-top: 20px; }
.pager a { flex: 1; background: linear-gradient(160deg, rgba(13,22,40,.7), rgba(8,13,25,.85));
  border: 1px solid var(--line); padding: 16px 20px;
  transition: transform .2s, border-color .2s, box-shadow .25s; }
.pager a:hover { text-decoration: none; border-color: var(--hud-dim); box-shadow: var(--glow-soft);
  transform: translateY(-2px); }
.pager a.next { text-align: right; }
.pager .dir { display: block; font: 600 11px var(--mono); letter-spacing: .2em; text-transform: uppercase;
  color: var(--txt-dim); margin-bottom: 5px; }
.pager .dir::before { content: "◂ "; } .pager a.next .dir::before { content: ""; }
.pager a.next .dir::after { content: " ▸"; }
.pager .ttl { font-weight: 700; color: var(--txt); font-size: 15px; letter-spacing: .3px; }

/* 返回顶部 */
.back-top { position: fixed; right: 26px; bottom: 26px; width: 46px; height: 46px; z-index: 55;
  border: 1px solid var(--hud-dim); background: rgba(8,15,28,.85); color: var(--hud);
  font-size: 17px; cursor: pointer; clip-path: var(--clip-corner);
  box-shadow: var(--glow-soft); opacity: 0; pointer-events: none; transition: opacity .25s, background .2s; }
.back-top.show { opacity: 1; pointer-events: auto; }
.back-top:hover { background: rgba(62,230,255,.15); }

/* 页脚 */
.footer { text-align: center; color: var(--txt-dim); font: 400 12.5px/1.8 var(--mono);
  letter-spacing: .06em; padding: 54px 20px 36px; }
.footer::before { content: "— ◈ 系统终端 ◈ —"; display: block; color: var(--hud-dim);
  font-size: 11px; margin-bottom: 12px; letter-spacing: .4em; }
.footer a { color: var(--hud-dim); }
.footer a:hover { color: var(--hud); }

/* 学习路径 */
.path-cols { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 16px; margin-top: 6px; }
.path-col { background: linear-gradient(165deg, rgba(15,26,47,.85), rgba(8,14,28,.9));
  border: 1px solid var(--line); padding: 22px; clip-path: var(--clip-corner); }
.path-col .no { font: 700 11px/1 var(--mono); letter-spacing: .24em; color: var(--amber); }
.path-col h3 { font-size: 16px; margin: 10px 0 8px; letter-spacing: .5px; color: var(--txt); }
.path-col p { font-size: 13.5px; color: var(--txt-dim); line-height: 1.8; }
.path-col p b { color: var(--hud); font-weight: 600; }

/* 滚动条 */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--bg0); }
::-webkit-scrollbar-thumb { background: rgba(62,230,255,.18); border-radius: 5px;
  border: 2px solid var(--bg0); }
::-webkit-scrollbar-thumb:hover { background: rgba(62,230,255,.35); }

@media (max-width: 640px) {
  body { font-size: 15.5px; }
  .hero-inner { padding: 56px 20px 50px; }
  .wrap, .layout, .topbar-inner { padding-left: 18px; padding-right: 18px; }
  .prose { font-size: 15.5px; }
  .grid { grid-template-columns: 1fr; }
  .pager { flex-direction: column; }
  .article-head h1 { font-size: 24px; }
}
/* 减弱动效偏好 */
@media (prefers-reduced-motion: reduce) {
  .brand-mark::after, .hero::before, .ch-card::before, .read-progress i { animation: none !important; transition: none !important; }
  html { scroll-behavior: auto; }
}