*{box-sizing:border-box}
body{margin:0;background:var(--bg);color:var(--ink);font-family:"Manrope","Inter",system-ui,sans-serif;line-height:1.55;padding:0 0 80px}
a{color:var(--cyan)}
header{padding:38px 20px 18px;text-align:center;background:linear-gradient(180deg,var(--bg2),transparent);border-bottom:1px solid var(--line)}
header .tag{color:var(--cyan);font-family:"JetBrains Mono",monospace;font-size:12px;letter-spacing:1px;text-transform:uppercase}
header h1{margin:6px 0 4px;font-size:28px;letter-spacing:-.5px}
header p{color:var(--muted);margin:6px auto 0;font-size:15px;max-width:720px}
.wrap{max-width:1160px;margin:0 auto;padding:0 20px}
.railwrap{max-width:1160px;margin:18px auto 0;padding:0 20px}
.rail{display:flex;gap:8px;flex-wrap:wrap;align-items:stretch}
.rail a{flex:1 1 120px;min-width:120px;text-decoration:none;display:block;border:1px solid var(--line);border-radius:10px;padding:9px 12px;background:var(--panel);transition:.14s}
.rail a:hover{border-color:var(--cyan);transform:translateY(-2px)}
.rail a .rn{font-family:"JetBrains Mono",monospace;font-size:11px;color:var(--muted)}
.rail a .rt{font-size:13px;color:var(--ink);font-weight:700;margin-top:2px;line-height:1.25}
.rail a.cur{border-color:var(--cyan);background:linear-gradient(180deg,rgba(34,211,238,.12),transparent)}
.rail a.cur .rn{color:var(--cyan)}
@media(max-width:760px){.rail a{flex:1 1 45%;min-width:0}}
.topnav{max-width:1160px;margin:14px auto 0;padding:0 20px}
.nav-back{display:inline-flex;align-items:center;gap:7px;text-decoration:none;font-family:"JetBrains Mono",monospace;font-size:13px;padding:7px 14px;border-radius:9px;border:1px solid var(--line);background:var(--panel);color:var(--muted)}
.nav-back:hover{border-color:var(--cyan);color:var(--cyan);background:rgba(34,211,238,.06)}
.intro{margin-top:28px}
.hook{font-size:16px;color:var(--ink);line-height:1.7;padding:14px 18px;background:var(--panel);border:1px solid var(--line);border-radius:10px;border-left:3px solid var(--cyan)}
.section{margin-top:46px}
.sec-head{display:flex;align-items:baseline;gap:14px;flex-wrap:wrap;margin-bottom:6px}
.sec-num{font-family:"JetBrains Mono",monospace;font-size:13px;color:var(--cyan);border:1px solid var(--line);border-radius:8px;padding:4px 10px;background:var(--bg2)}
.sec-head h2{font-size:23px;margin:0;letter-spacing:-.3px}
.sec-sub{color:var(--muted);font-size:14.5px;margin:4px 0 0;max-width:820px;line-height:1.6}
.badges{display:flex;gap:7px;flex-wrap:wrap;margin:12px 0 2px}
.b{font-family:"JetBrains Mono",monospace;font-size:11px;letter-spacing:.04em;text-transform:uppercase;padding:4px 10px;border-radius:999px;border:1px solid var(--line)}
.b.fgos{color:var(--green);background:rgba(52,211,153,.08);border-color:rgba(52,211,153,.35)}
.b.exam{color:var(--amber);background:rgba(252,211,77,.08);border-color:rgba(252,211,77,.35)}
.b.fop{color:var(--violet);background:rgba(167,139,250,.08);border-color:rgba(167,139,250,.35)}
.theory-block{background:rgba(34,211,238,.03);border-left:3px solid var(--cyan);padding:16px 20px;border-radius:0 10px 10px 0;margin:16px 0}
.example-box{background:rgba(252,211,77,.04);border-left:3px solid var(--amber);padding:16px 20px;border-radius:0 10px 10px 0;margin:16px 0}
.iv-shell{background:var(--panel);border:1px solid var(--line);border-radius:14px;padding:24px;margin:28px 0;position:relative;overflow:hidden}
.iv-shell::before{content:'';position:absolute;top:0;left:0;right:0;height:3px;background:linear-gradient(90deg,var(--cyan),var(--amber))}
.iv-head{display:flex;align-items:center;gap:10px;margin-bottom:18px}
.iv-head .iv-icon{width:34px;height:34px;border-radius:10px;display:flex;align-items:center;justify-content:center;font-size:17px;background:var(--bg2);border:1px solid var(--line)}
.iv-head .iv-title{font-weight:700;font-size:16px}
.iv-body{min-height:80px}
.btn-c{padding:10px 20px;border-radius:9px;border:1px solid var(--line);background:var(--panel2);color:var(--ink);font-weight:600;font-size:13px;cursor:pointer;transition:.14s;display:inline-flex;align-items:center;gap:6px}
.btn-c:hover{border-color:var(--cyan);color:var(--cyan)}
.btn-c.primary{background:var(--cyan);color:#04222b;border-color:var(--cyan)}
.btn-c.primary:hover{filter:brightness(1.08)}
.result-box{padding:12px 16px;border-radius:8px;margin:12px 0;font-size:14px}
.result-box.ok{background:rgba(52,211,153,.08);border:1px solid rgba(52,211,153,.35);color:var(--green)}
.result-box.fail{background:rgba(248,113,113,.08);border:1px solid rgba(248,113,113,.35);color:var(--red)}
.diagram-box{background:var(--panel);border:1px solid var(--line);border-radius:12px;padding:20px;margin:18px 0;overflow-x:auto}
.dt{width:100%;border-collapse:collapse;margin:8px 0;font-size:14px}
.dt th,.dt td{padding:8px 12px;border:1px solid var(--line);text-align:left}
.dt th{background:var(--bg2);color:var(--cyan);font-size:12px;text-transform:uppercase;letter-spacing:.05em}
.dt tr:hover{background:rgba(34,211,238,.03)}
.grid3{display:grid;grid-template-columns:repeat(3,1fr);gap:14px;margin:16px 0}
.grid2{display:grid;grid-template-columns:repeat(2,1fr);gap:14px;margin:16px 0}
.card-sm{background:var(--panel2);border:1px solid var(--line);border-radius:10px;padding:15px;text-align:center}
.card-sm .cs-num{font-family:"JetBrains Mono",monospace;font-size:28px;color:var(--cyan);font-weight:700;line-height:1}
.card-sm .cs-label{font-size:13px;color:var(--muted);margin-top:6px}
input[type=range]{-webkit-appearance:none;width:100%;height:6px;background:var(--bg2);border-radius:4px;outline:none}
input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;width:18px;height:18px;background:var(--cyan);border-radius:50%;cursor:pointer}
input[type=text],input[type=number]{background:var(--bg2);border:1px solid var(--line);border-radius:8px;color:var(--ink);padding:8px 12px;font-family:"JetBrains Mono",monospace;font-size:14px;width:120px}
.palette-grid{display:grid;gap:2px;margin:12px 0}
.palette-cell{aspect-ratio:1;border-radius:3px;transition:.1s}
.chart-wrap{background:var(--panel);border:1px solid var(--line);border-radius:12px;padding:16px;margin:16px 0;height:260px}
.feedback{padding:10px 14px;border-radius:8px;margin:8px 0;font-size:13px}
.feedback.good{background:rgba(52,211,153,.1);border:1px solid rgba(52,211,153,.3);color:var(--green)}
.feedback.bad{background:rgba(248,113,113,.1);border:1px solid rgba(248,113,113,.3);color:var(--red)}
.graph-canvas{width:100%;height:320px;background:var(--bg2);border-radius:10px;border:1px solid var(--line);margin:12px 0;display:block}