:root{
  --bg:#0d1117; --bg-2:#161b22; --bg-3:#1f2937; --panel:#0f1620;
  --fg:#e6edf3; --fg-2:#9aa6b2; --fg-dim:#6b7785;
  --accent:#58a6ff; --accent-2:#7ee787; --warn:#f0883e; --danger:#f85149;
  --border:#30363d; --code-bg:#0a0e14; --kbd:#21262d;
  --shadow:0 4px 16px rgba(0,0,0,.4);
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  font:15px/1.65 -apple-system,BlinkMacSystemFont,"SF Pro Text","Segoe UI",Helvetica,Arial,sans-serif;
  background:var(--bg); color:var(--fg);
  -webkit-font-smoothing:antialiased;
  padding-top:env(safe-area-inset-top);
  padding-bottom:env(safe-area-inset-bottom);
}
code,pre,.mono{font-family:"JetBrains Mono","Fira Code","SF Mono",Menlo,Consolas,monospace}
a{color:var(--accent);text-decoration:none}
a:hover{text-decoration:underline}
button{font-family:inherit}

.app{display:grid;grid-template-columns:300px 1fr;min-height:100vh}
.sidebar{
  background:var(--bg-2);border-right:1px solid var(--border);
  position:sticky;top:0;height:100vh;overflow-y:auto;
  padding:16px 14px;
}
.main{padding:24px 32px 80px;max-width:1000px;width:100%;margin:0 auto}
@media (max-width:900px){
  .app{grid-template-columns:1fr}
  .sidebar{position:fixed;left:-100%;top:0;width:85%;max-width:320px;z-index:100;transition:left .2s;box-shadow:var(--shadow)}
  .sidebar.open{left:0}
  .main{padding:14px 16px 80px}
  .topbar-mobile{display:flex !important}
}

.topbar{
  position:sticky;top:0;z-index:50;background:rgba(13,17,23,.92);
  backdrop-filter:blur(10px);-webkit-backdrop-filter:blur(10px);
  border-bottom:1px solid var(--border);
  padding:10px 16px;display:flex;gap:12px;align-items:center;
}
.topbar h1{font-size:15px;margin:0;font-weight:600;color:var(--fg);flex:1;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.topbar .progress-wrap{flex:0 0 140px}
.topbar-mobile{display:none}
.menu-btn{
  background:var(--bg-3);color:var(--fg);border:1px solid var(--border);
  width:36px;height:36px;border-radius:8px;cursor:pointer;font-size:18px;
}

.sidebar h2{
  font-size:11px;text-transform:uppercase;letter-spacing:1.5px;
  color:var(--fg-dim);margin:18px 8px 6px;font-weight:600;
}
.sidebar h2:first-child{margin-top:4px}
.brand{
  font-weight:700;font-size:15px;color:var(--fg);
  padding:10px 12px;margin-bottom:10px;border-radius:8px;
  background:linear-gradient(135deg,#1f6feb22,#7ee78722);
  border:1px solid var(--border);
}
.brand small{display:block;color:var(--fg-dim);font-size:11px;font-weight:400;margin-top:2px}
.search-box{
  width:100%;padding:8px 10px;background:var(--code-bg);
  border:1px solid var(--border);border-radius:8px;color:var(--fg);
  font-size:13px;outline:none;
}
.search-box:focus{border-color:var(--accent)}
.nav-list{list-style:none;padding:0;margin:4px 0}
.nav-list li{margin:1px 0}
.nav-list a{
  display:flex;align-items:center;gap:8px;
  padding:6px 10px;border-radius:6px;color:var(--fg-2);
  font-size:13px;line-height:1.35;
}
.nav-list a:hover{background:var(--bg-3);color:var(--fg);text-decoration:none}
.nav-list a.active{background:var(--bg-3);color:var(--accent);border-left:2px solid var(--accent)}
.nav-list a.done::before{content:"✓";color:var(--accent-2);font-weight:bold;margin-right:2px;width:12px;display:inline-block}
.nav-list a:not(.done)::before{content:"○";color:var(--fg-dim);margin-right:2px;font-size:11px;width:12px;display:inline-block}
.nav-num{color:var(--fg-dim);font-size:11px;min-width:22px}

.progress-bar{
  height:6px;background:var(--bg-3);border-radius:3px;overflow:hidden;
  border:1px solid var(--border);
}
.progress-fill{
  height:100%;background:linear-gradient(90deg,var(--accent),var(--accent-2));
  width:0%;transition:width .3s;
}
.progress-label{font-size:11px;color:var(--fg-dim);margin-top:4px;text-align:right}

section.chunk{
  background:var(--bg-2);border:1px solid var(--border);border-radius:12px;
  padding:24px 28px;margin:20px 0;scroll-margin-top:80px;
}
section.chunk[hidden]{display:none}
section.chunk h1{
  font-size:28px;margin:0 0 8px;color:var(--fg);
  display:flex;align-items:center;gap:12px;flex-wrap:wrap;
}
section.chunk h2{font-size:20px;margin:20px 0 10px;color:var(--fg);border-bottom:1px solid var(--border);padding-bottom:6px}
section.chunk h3{font-size:16px;margin:16px 0 8px;color:var(--accent)}
section.chunk h4{font-size:14px;margin:14px 0 6px;color:var(--accent-2)}
section.chunk p{margin:8px 0}
section.chunk ul,section.chunk ol{margin:8px 0;padding-left:24px}
section.chunk li{margin:3px 0}
section.chunk strong{color:var(--fg)}
section.chunk em{color:var(--accent-2);font-style:normal}
section.chunk hr{border:none;border-top:1px solid var(--border);margin:18px 0}
@media (max-width:900px){
  section.chunk{padding:18px 16px}
  section.chunk h1{font-size:22px}
}

.sec-header{
  display:flex;align-items:center;gap:12px;margin-bottom:14px;
  padding-bottom:14px;border-bottom:1px solid var(--border);flex-wrap:wrap;
}
.sec-num{
  width:36px;height:36px;border-radius:50%;
  background:linear-gradient(135deg,var(--accent),var(--accent-2));
  color:#0d1117;font-weight:700;display:flex;align-items:center;justify-content:center;
  flex-shrink:0;
}
.sec-title{flex:1;min-width:0}
.sec-meta{font-size:12px;color:var(--fg-dim)}

pre{
  background:var(--code-bg);border:1px solid var(--border);border-radius:8px;
  padding:12px 14px;margin:10px 0;overflow-x:auto;position:relative;
  font-size:13px;line-height:1.5;
}
pre code{display:block;color:#cdd9e5}
p code,li code,td code,h3 code,h4 code,summary code{
  background:var(--code-bg);padding:2px 6px;border-radius:4px;
  font-size:.88em;color:var(--accent-2);border:1px solid var(--border);
}
.copy-btn{
  position:absolute;top:6px;right:6px;
  background:var(--bg-3);color:var(--fg-2);
  border:1px solid var(--border);border-radius:6px;
  padding:4px 10px;font-size:11px;cursor:pointer;opacity:0;transition:opacity .15s;
}
pre:hover .copy-btn,pre:focus-within .copy-btn,.copy-btn.copied{opacity:1}
.copy-btn:hover{background:var(--accent);color:#0d1117;border-color:var(--accent)}
.copy-btn.copied{background:var(--accent-2);color:#0d1117;border-color:var(--accent-2)}

table{
  width:100%;border-collapse:collapse;margin:12px 0;
  background:var(--panel);border-radius:8px;overflow:hidden;
  font-size:13px;
}
th,td{padding:8px 12px;text-align:left;border-bottom:1px solid var(--border);vertical-align:top}
th{background:var(--bg-3);color:var(--fg);font-weight:600;font-size:12px;text-transform:uppercase;letter-spacing:.5px}
tr:last-child td{border-bottom:none}
tr:hover td{background:var(--bg-3)}
@media (max-width:900px){
  table{font-size:12px}
  th,td{padding:6px 8px}
}

kbd{
  background:var(--kbd);border:1px solid var(--border);border-bottom-width:2px;
  border-radius:4px;padding:1px 6px;font-family:inherit;font-size:.85em;
  color:var(--fg);box-shadow:0 1px 0 rgba(0,0,0,.3);
}

.callout{
  border-left:4px solid var(--accent);background:var(--panel);
  border-radius:6px;padding:10px 14px;margin:12px 0;
}
.callout.tip{border-color:var(--accent-2)}
.callout.warn{border-color:var(--warn)}
.callout.danger{border-color:var(--danger)}
.callout-title{font-weight:600;margin-bottom:4px;display:flex;align-items:center;gap:6px}

details.collapse{
  background:var(--panel);border:1px solid var(--border);border-radius:8px;
  margin:12px 0;padding:0;
}
details.collapse summary{
  cursor:pointer;padding:10px 14px;font-weight:600;color:var(--fg);
  list-style:none;display:flex;align-items:center;gap:8px;
  user-select:none;
}
details.collapse summary::-webkit-details-marker{display:none}
details.collapse summary::before{
  content:"▶";font-size:10px;transition:transform .2s;color:var(--fg-dim);
}
details.collapse[open] summary::before{transform:rotate(90deg)}
details.collapse summary:hover{background:var(--bg-3)}
details.collapse[open] summary{border-bottom:1px solid var(--border)}
details.collapse > div{padding:12px 14px}

.quiz{
  background:linear-gradient(135deg,#1f6feb15,#7ee78715);
  border:1px solid var(--accent);border-radius:12px;
  padding:18px 20px;margin:20px 0;
}
.quiz-title{
  font-size:13px;color:var(--accent);font-weight:700;
  text-transform:uppercase;letter-spacing:1.5px;margin-bottom:12px;
  display:flex;align-items:center;gap:8px;
}
.quiz-q{font-weight:600;margin-bottom:10px;color:var(--fg)}
.quiz-options{display:flex;flex-direction:column;gap:6px}
.quiz-opt{
  background:var(--bg-3);border:1px solid var(--border);border-radius:8px;
  padding:10px 14px;cursor:pointer;transition:all .15s;
  text-align:left;color:var(--fg-2);font-size:14px;font-family:inherit;
}
.quiz-opt:hover{background:var(--bg-2);color:var(--fg);border-color:var(--accent)}
.quiz-opt.correct{background:#1a3a2a;border-color:var(--accent-2);color:var(--accent-2)}
.quiz-opt.wrong{background:#3a1a1a;border-color:var(--danger);color:var(--danger)}
.quiz-opt:disabled{cursor:not-allowed}
.quiz-explain{
  margin-top:10px;padding:10px 12px;background:var(--bg-3);
  border-radius:6px;font-size:13px;color:var(--fg-2);display:none;
  border-left:3px solid var(--accent-2);
}
.quiz-explain.show{display:block}

.completion{
  display:flex;align-items:center;gap:12px;justify-content:space-between;
  margin-top:24px;padding:14px 18px;background:var(--panel);
  border:1px solid var(--border);border-radius:8px;flex-wrap:wrap;
}
.btn{
  background:var(--accent);color:#0d1117;border:none;
  border-radius:8px;padding:8px 16px;cursor:pointer;font-weight:600;
  font-size:13px;transition:all .15s;font-family:inherit;
}
.btn:hover{background:#79b8ff;transform:translateY(-1px)}
.btn.secondary{background:var(--bg-3);color:var(--fg);border:1px solid var(--border)}
.btn.secondary:hover{background:var(--bg-2)}
.btn.done{background:var(--accent-2);color:#0d1117}

.cheat-filters{display:flex;gap:6px;flex-wrap:wrap;margin:12px 0}
.cheat-filter{
  background:var(--bg-3);color:var(--fg-2);border:1px solid var(--border);
  border-radius:16px;padding:5px 12px;font-size:12px;cursor:pointer;
  font-family:inherit;
}
.cheat-filter.active{background:var(--accent);color:#0d1117;border-color:var(--accent)}
.cheat-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:12px;margin-top:12px}
.cheat-card{
  background:var(--panel);border:1px solid var(--border);border-radius:8px;
  padding:12px 14px;
}
.cheat-card[hidden]{display:none}
.cheat-card-title{
  font-size:11px;text-transform:uppercase;letter-spacing:1px;color:var(--fg-dim);
  margin-bottom:8px;display:flex;justify-content:space-between;align-items:center;
}
.cheat-card-title .tag{
  background:var(--bg-3);color:var(--accent);padding:2px 6px;border-radius:4px;
  font-size:10px;font-weight:600;
}
.cheat-card pre{margin:0;font-size:12px;border:none;background:var(--code-bg);padding:8px}

.hero{
  background:linear-gradient(135deg,#1f6feb22 0%,#7ee78711 100%);
  border:1px solid var(--border);border-radius:16px;padding:30px;
  margin-bottom:24px;
}
.hero h1{font-size:32px;margin:0 0 8px;background:linear-gradient(90deg,var(--accent),var(--accent-2));-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent}
.hero p{color:var(--fg-2);margin:6px 0}
.hero .conn{font-family:"SF Mono",monospace;background:var(--code-bg);padding:8px 12px;border-radius:6px;display:inline-block;font-size:13px;border:1px solid var(--border);margin-top:8px}
@media (max-width:900px){.hero{padding:20px}.hero h1{font-size:24px}}

.path-map{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));gap:10px;margin:16px 0}
.path-step{
  background:var(--panel);border:1px solid var(--border);border-radius:10px;
  padding:14px 12px;text-align:center;font-size:13px;
}
.path-step .num{font-size:22px;font-weight:700;color:var(--accent);display:block;margin-bottom:4px}
.path-step .label{color:var(--fg-2);font-size:12px}

.badges{display:flex;gap:8px;flex-wrap:wrap;margin-top:12px}
.badge-chip{
  background:var(--bg-3);border:1px solid var(--border);border-radius:20px;
  padding:4px 12px;font-size:11px;color:var(--fg-dim);
  display:flex;align-items:center;gap:6px;
}
.badge-chip.unlocked{
  background:linear-gradient(135deg,#1f6feb33,#7ee78733);
  border-color:var(--accent-2);color:var(--accent-2);
}

.search-results{
  background:var(--bg-2);border:1px solid var(--border);border-radius:8px;
  margin-top:8px;max-height:300px;overflow-y:auto;display:none;
  position:absolute;width:calc(100% - 28px);z-index:10;box-shadow:var(--shadow);
}
.search-results.show{display:block}
.search-result-item{padding:8px 12px;border-bottom:1px solid var(--border);cursor:pointer;font-size:13px}
.search-result-item:hover{background:var(--bg-3)}
.search-result-item:last-child{border-bottom:none}
.search-result-item .meta{font-size:11px;color:var(--fg-dim);margin-top:2px}

mark{background:var(--accent);color:#0d1117;padding:0 2px;border-radius:2px}

.toc-list{list-style:none;padding:0}
.toc-list li{margin:4px 0}
.toc-list a{display:block;padding:6px 10px;border-radius:6px;background:var(--panel);border:1px solid var(--border)}
.toc-list a:hover{background:var(--bg-3);text-decoration:none}

.loading{text-align:center;padding:40px;color:var(--fg-dim)}

@media print{
  .sidebar,.topbar,.copy-btn,.menu-btn,.completion,.search-results,.cheat-filters{display:none !important}
  .app{grid-template-columns:1fr}
  section.chunk{display:block !important;page-break-inside:avoid}
}

::-webkit-scrollbar{width:8px;height:8px}
::-webkit-scrollbar-track{background:var(--bg)}
::-webkit-scrollbar-thumb{background:var(--bg-3);border-radius:4px}
::-webkit-scrollbar-thumb:hover{background:var(--border)}