:root{
  --bg:#07111f;
  --bg2:#0d1728;
  --panel:rgba(255,255,255,.08);
  --panel2:rgba(255,255,255,.05);
  --border:rgba(255,255,255,.12);
  --text:#ecf3ff;
  --muted:#a9b6cf;
  --primary:#38bdf8;
  --secondary:#8b5cf6;
  --success:#22c55e;
  --warning:#f59e0b;
  --danger:#ef4444;
  --shadow:0 18px 40px rgba(0,0,0,.28);
  --hero:linear-gradient(135deg,#0ea5e9 0%, #8b5cf6 45%, #22c55e 100%);
}
body.light{
  --bg:#f3f7ff;
  --bg2:#e8f0ff;
  --panel:rgba(255,255,255,.88);
  --panel2:#ffffff;
  --border:rgba(10,20,40,.08);
  --text:#172033;
  --muted:#5b6883;
  --shadow:0 14px 36px rgba(11,22,44,.10);
  --hero:linear-gradient(135deg,#38bdf8 0%, #818cf8 50%, #4ade80 100%);
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;
  font-family:"Segoe UI","Noto Sans TC","PingFang TC","Microsoft JhengHei",sans-serif;
  color:var(--text);
  background:radial-gradient(circle at top left, rgba(56,189,248,.16), transparent 25%),radial-gradient(circle at top right, rgba(139,92,246,.18), transparent 30%),linear-gradient(180deg,var(--bg) 0%, var(--bg2) 100%);
}
a{color:var(--primary);text-decoration:none}
code,pre{font-family:Consolas,Monaco,monospace}
.app{display:grid;grid-template-columns:280px 1fr;min-height:100vh}
.sidebar{position:sticky;top:0;height:100vh;overflow:auto;padding:18px;background:rgba(7,17,31,.72);backdrop-filter:blur(16px);border-right:1px solid var(--border)}
body.light .sidebar{background:rgba(255,255,255,.72)}
.brand{display:flex;align-items:center;gap:12px;margin-bottom:18px}
.logo{width:48px;height:48px;border-radius:15px;display:grid;place-items:center;background:var(--hero);font-weight:800;color:#fff;box-shadow:var(--shadow)}
.brand h1{font-size:1.02rem;margin:0}
.brand small{display:block;color:var(--muted);margin-top:4px}
.search{position:relative;margin-bottom:16px}
.search input{width:100%;padding:12px 12px 12px 40px;border-radius:14px;border:1px solid var(--border);background:var(--panel);color:var(--text);outline:none}
.search span{position:absolute;left:13px;top:50%;transform:translateY(-50%);opacity:.7}
.nav-group{margin-top:16px}
.nav-title{color:var(--muted);font-size:.82rem;text-transform:uppercase;letter-spacing:.08em;margin:0 0 10px}
.nav{display:flex;flex-direction:column;gap:8px}
.nav a{padding:10px 12px;border-radius:12px;color:var(--text);border:1px solid transparent;transition:.2s}
.nav a:hover,.nav a.active{background:var(--panel);border-color:var(--border);transform:translateX(2px)}
.nav small{display:block;color:var(--muted);margin-top:3px}
.side-card{margin-top:18px;background:var(--panel);border:1px solid var(--border);border-radius:18px;padding:14px;box-shadow:var(--shadow)}
.btn{display:inline-flex;align-items:center;gap:8px;padding:11px 15px;border-radius:14px;border:none;background:linear-gradient(135deg,var(--primary),var(--secondary));color:#fff;font-weight:700;cursor:pointer;box-shadow:var(--shadow)}
.btn.ghost{background:var(--panel);color:var(--text);border:1px solid var(--border);box-shadow:none}
.btn.success{background:linear-gradient(135deg,#22c55e,#16a34a)}
.main{padding:24px}
.topbar{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;margin-bottom:20px}
.breadcrumb{color:var(--muted);font-size:.92rem}
.actions{display:flex;gap:10px;flex-wrap:wrap}
.hero{background:var(--hero);color:#fff;border-radius:28px;padding:32px;box-shadow:var(--shadow);position:relative;overflow:hidden}
.hero:before{content:"";position:absolute;inset:auto -40px -40px auto;width:220px;height:220px;border-radius:50%;background:rgba(255,255,255,.14);filter:blur(8px)}
.hero-grid{display:grid;grid-template-columns:1.15fr .85fr;gap:22px;align-items:center}
.hero h2{font-size:2.15rem;line-height:1.15;margin:0 0 10px}
.hero p{line-height:1.85;margin:0;color:rgba(255,255,255,.92)}
.badges{display:flex;gap:10px;flex-wrap:wrap;margin:18px 0}
.badge{padding:8px 12px;border-radius:999px;background:rgba(255,255,255,.14);border:1px solid rgba(255,255,255,.18);font-size:.9rem}
.hero-box{background:rgba(255,255,255,.12);border:1px solid rgba(255,255,255,.18);border-radius:22px;padding:18px;backdrop-filter:blur(10px)}
.stats{display:grid;grid-template-columns:repeat(2,1fr);gap:12px;margin-top:14px}
.stat{padding:14px;border-radius:18px;background:rgba(255,255,255,.12)}
.stat strong{display:block;font-size:1.25rem}
.section-title{display:flex;justify-content:space-between;align-items:end;gap:12px;flex-wrap:wrap;margin:28px 0 14px}
.section-title h3{margin:0;font-size:1.55rem}
.section-title p{margin:0;color:var(--muted)}
.grid{display:grid;gap:18px}
.grid-3{grid-template-columns:repeat(3,1fr)}
.grid-4{grid-template-columns:repeat(4,1fr)}
.panel{background:var(--panel);border:1px solid var(--border);border-radius:24px;padding:22px;box-shadow:var(--shadow);backdrop-filter:blur(16px)}
.card{background:linear-gradient(180deg, rgba(255,255,255,.08), rgba(255,255,255,.04));border:1px solid var(--border);border-radius:22px;padding:20px}
.icon{width:48px;height:48px;border-radius:14px;display:grid;place-items:center;background:linear-gradient(135deg,var(--primary),var(--secondary));color:#fff;font-size:1.35rem;box-shadow:var(--shadow);margin-bottom:12px}
.card p,.muted{color:var(--muted);line-height:1.8}
.lesson{background:var(--panel);border:1px solid var(--border);border-radius:22px;overflow:hidden}
.lesson-head{display:flex;justify-content:space-between;align-items:center;gap:16px;flex-wrap:wrap;padding:18px 20px;border-bottom:1px solid var(--border);background:linear-gradient(180deg, rgba(255,255,255,.05), rgba(255,255,255,.02))}
.lesson-head h4{margin:0 0 6px;font-size:1.16rem}
.lesson-head p{margin:0;color:var(--muted)}
.lesson-body{padding:20px}
.tag{padding:6px 10px;border-radius:999px;font-size:.82rem;font-weight:700}
.tag.beginner{background:rgba(34,197,94,.15);color:#4ade80}
.tag.middle{background:rgba(245,158,11,.16);color:#fbbf24}
.tag.advanced{background:rgba(239,68,68,.15);color:#f87171}
.chips{display:flex;gap:8px;flex-wrap:wrap;margin-top:8px}
.chip{padding:7px 10px;border-radius:999px;background:rgba(255,255,255,.06);border:1px solid var(--border);font-size:.85rem}
.code-card{margin-top:14px;border:1px solid rgba(255,255,255,.08);border-radius:18px;overflow:hidden;background:#0b1220}
.code-head{display:flex;justify-content:space-between;align-items:center;gap:8px;padding:12px 14px;background:#111827;color:#dbeafe;border-bottom:1px solid rgba(255,255,255,.08)}
.code-btn{border:1px solid rgba(255,255,255,.1);background:#1f2937;color:#fff;padding:7px 10px;border-radius:10px;cursor:pointer}
pre{margin:0;padding:16px 18px;overflow:auto;line-height:1.7;color:#e5efff}
.note{margin-top:14px;padding:14px 16px;border-left:4px solid var(--primary);border-radius:14px;background:rgba(56,189,248,.10);line-height:1.8}
.example-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:18px}
.example-card{background:var(--panel);border:1px solid var(--border);border-radius:22px;overflow:hidden}
.example-card .inner{padding:18px}
.preview{padding:16px;border-top:1px solid var(--border);background:rgba(255,255,255,.03)}
.preview-box{background:#fff;color:#111827;border-radius:16px;padding:14px;min-height:70px}
.table-wrap{overflow:auto;border:1px solid var(--border);border-radius:18px}
table{width:100%;border-collapse:collapse;min-width:720px;background:var(--panel)}
th,td{padding:14px 16px;border-bottom:1px solid var(--border);text-align:left}
th{background:rgba(255,255,255,.06)}
details{background:var(--panel);border:1px solid var(--border);border-radius:18px;padding:16px 18px;margin-bottom:12px}
details summary{cursor:pointer;font-weight:700}
details p{color:var(--muted);line-height:1.8}
.quiz-wrap{display:grid;grid-template-columns:1fr 320px;gap:18px}
.quiz-q{padding:18px;border-radius:18px;background:rgba(255,255,255,.05);border:1px solid var(--border);margin-bottom:14px}
.option{display:block;padding:10px 12px;border:1px solid var(--border);border-radius:12px;margin-bottom:10px;cursor:pointer}
.option:hover{background:rgba(255,255,255,.06)}
.progress{height:12px;background:rgba(255,255,255,.08);border-radius:999px;overflow:hidden;border:1px solid var(--border)}
.progress span{display:block;height:100%;width:0;background:linear-gradient(90deg,var(--primary),var(--success));transition:.3s}
.footer{margin-top:28px;padding:18px 0 6px;color:var(--muted);text-align:center}
.mobile-menu{display:none}
.hidden{display:none !important}
@media (max-width:1200px){.grid-4{grid-template-columns:repeat(2,1fr)}.quiz-wrap{grid-template-columns:1fr}.example-grid{grid-template-columns:1fr}}
@media (max-width:992px){.app{grid-template-columns:1fr}.sidebar{position:fixed;left:-320px;z-index:999;width:280px;transition:.3s}.sidebar.open{left:0}.mobile-menu{display:inline-flex}.hero-grid,.grid-3{grid-template-columns:1fr}}
@media (max-width:640px){.main{padding:16px}.hero{padding:24px}.hero h2{font-size:1.75rem}.grid-4{grid-template-columns:1fr}}