:root{
  --bg:#0e1117; --panel:#161b25; --panel2:#1d2432; --line:#2a3346;
  --ink:#e8edf6; --muted:#aab6ca; --dim:#8b98b2;
  --brand:#3b6cf6; --brand2:#7aa2ff; --ok:#2fbf71; --warn:#f0b429; --bad:#ef4d5a;
  --radius:14px; --shadow:0 6px 24px rgba(0,0,0,.35);
  --headH:62px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
html,body{margin:0;padding:0}
body{
  background:var(--bg); color:var(--ink);
  font:16px/1.6 -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  -webkit-font-smoothing:antialiased; overflow-x:hidden;
}
a{color:var(--brand2);text-decoration:none}
a:hover{text-decoration:underline}
img{max-width:100%}
.wrap{max-width:1100px;margin:0 auto;padding:0 18px;width:100%}
main.wrap{padding-bottom:40px}

/* ---------- header (height-auto so a wrapping nav can never overlap) ---------- */
header.top{position:sticky;top:0;z-index:50;background:rgba(14,17,23,.94);backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}
header.top .bar{display:flex;align-items:center;gap:12px;min-height:var(--headH);padding:8px 0;flex-wrap:wrap}
.brand{font-weight:700;letter-spacing:.2px;display:flex;align-items:center;gap:9px;font-size:15px}
.brand .dot{width:11px;height:11px;border-radius:3px;background:linear-gradient(135deg,var(--brand),var(--brand2));flex:0 0 11px}
nav.main{display:flex;gap:4px;margin-left:auto;flex-wrap:wrap;justify-content:flex-end}
nav.main a{padding:7px 11px;border-radius:9px;color:var(--muted);font-weight:600;font-size:14px;white-space:nowrap}
nav.main a:hover{background:var(--panel);color:var(--ink);text-decoration:none}
nav.main a.on{background:var(--panel2);color:var(--ink)}
@media(max-width:560px){
  header.top .bar{gap:8px}
  .brand{font-size:13.5px}
  nav.main{width:100%;overflow-x:auto;flex-wrap:nowrap;justify-content:flex-start;margin-left:0;
           -webkit-overflow-scrolling:touch;scrollbar-width:none}
  nav.main::-webkit-scrollbar{display:none}
}

/* ---------- typography ---------- */
h1{font-size:clamp(24px,4.4vw,38px);line-height:1.18;margin:.3em 0}
h2{font-size:clamp(20px,3vw,25px);margin:1.2em 0 .5em}
h3{font-size:18px;margin:1.05em 0 .4em}
p{margin:.6em 0}
p.lead{color:var(--muted);font-size:clamp(16px,2.4vw,18px);max-width:72ch}
code{background:var(--panel2);padding:1px 5px;border-radius:5px;font-size:.92em}

/* ---------- blocks ---------- */
.grid{display:grid;gap:14px}
.cards{grid-template-columns:repeat(auto-fit,minmax(230px,1fr))}
.card{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:18px;min-width:0}
.card h3{margin:.1em 0 .35em}
.card p{color:var(--muted);margin:.3em 0;font-size:14.5px}
.btn{display:inline-flex;align-items:center;gap:8px;cursor:pointer;border:1px solid var(--line);
  background:var(--panel2);color:var(--ink);padding:11px 16px;border-radius:11px;font-weight:650;font-size:15px;line-height:1.1}
.btn:hover{border-color:var(--brand)}
.btn.primary{background:linear-gradient(135deg,var(--brand),var(--brand2));border-color:transparent;color:#08122c}
.btn.ghost{background:transparent}
.btn.sm{padding:7px 12px;font-size:13.5px;border-radius:9px}
.btn[disabled]{opacity:.45;cursor:not-allowed}
.pill{display:inline-block;padding:3px 9px;border-radius:999px;font-size:12px;font-weight:700;border:1px solid var(--line);color:var(--muted)}
.pill.v1{border-color:#3b4a6b;color:#9fb6ff}
.pill.v2{border-color:#3b6b52;color:#9fe6bd}
.pill.v3{border-color:#6b5a3b;color:#f0d59f}
.row{display:flex;gap:10px;flex-wrap:wrap;align-items:center}
input[type=text],input[type=search],select{background:var(--panel2);border:1px solid var(--line);color:var(--ink);
  border-radius:10px;padding:10px 12px;font:inherit;font-size:15px;max-width:100%}
select{cursor:pointer}
.muted{color:var(--muted)} .dim{color:var(--dim)} .small{font-size:13.5px}
hr{border:0;border-top:1px solid var(--line);margin:22px 0}
footer{border-top:1px solid var(--line);margin-top:40px;padding:20px 0 30px;color:var(--dim);font-size:13px}

/* ---------- library: sidebar + content ---------- */
.split{display:grid;grid-template-columns:290px minmax(0,1fr);gap:22px;align-items:start;padding-top:20px}
.side{position:sticky;top:calc(var(--headH) + 14px);max-height:calc(100vh - var(--headH) - 34px);
  overflow:auto;background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:10px}
.side .vol{margin:8px 0 2px;font-weight:700;font-size:12.5px;color:var(--muted);text-transform:uppercase;letter-spacing:.06em;padding:6px 8px}
.side a.item{display:block;padding:8px 9px;border-radius:8px;color:var(--ink);font-size:14px;padding-left:54px;position:relative}
.side a.item .code{position:absolute;left:10px;top:8px;color:#94a2bd;font-variant-numeric:tabular-nums;font-size:12.5px}
.side a.item:hover{background:var(--panel2);text-decoration:none}
.side a.item.on{background:var(--panel2);outline:1px solid var(--brand)}
.content{min-width:0}
.only-mobile{display:none}
@media(max-width:880px){
  .split{grid-template-columns:1fr}
  .side{display:none}
  .only-mobile{display:block}
}

/* ---------- article ---------- */
article.note{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:22px}
article.note h2:first-child{margin-top:0}
.note ul{padding-left:20px}
.note li{margin:6px 0}
.callout{border-left:3px solid var(--brand);background:var(--panel2);padding:12px 14px;border-radius:0 10px 10px 0;margin:14px 0}
.callout.tip{border-color:var(--ok)} .callout.warn{border-color:var(--warn)}
table{width:100%;border-collapse:collapse;font-size:14.5px;margin:10px 0}
th,td{text-align:left;padding:9px 10px;border-bottom:1px solid var(--line);vertical-align:top}
th{color:var(--muted);font-weight:650}

/* ---------- glossary ---------- */
.glist{display:grid;gap:10px;grid-template-columns:repeat(auto-fill,minmax(320px,1fr));margin:8px 0}
@media(max-width:520px){.glist{grid-template-columns:1fr}}
.gitem{background:var(--panel);border:1px solid var(--line);border-radius:12px;padding:14px;min-width:0}
.gitem h3{margin:0 0 5px;font-size:16px;display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.gitem .tag{font-size:12px;color:var(--muted);margin-top:6px}

/* ---------- exam ---------- */
.examhead{display:flex;gap:12px;align-items:center;flex-wrap:wrap;background:var(--panel);border:1px solid var(--line);
  border-radius:var(--radius);padding:12px 14px;position:sticky;top:calc(var(--headH) + 6px);z-index:20}
.timer{font-variant-numeric:tabular-nums;font-weight:750;font-size:20px}
.timer.low{color:var(--bad)}
.qbox{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:20px;margin-top:16px}
.qstem{font-size:17px;line-height:1.55;margin:8px 0 16px}
.opts{display:grid;gap:9px}
.opt{display:flex;gap:11px;align-items:flex-start;border:1px solid var(--line);background:var(--panel2);
  border-radius:11px;padding:12px 14px;cursor:pointer;min-width:0}
.opt:hover{border-color:var(--brand)}
.opt .k{width:26px;height:26px;flex:0 0 26px;border-radius:6px;background:var(--bg);border:1px solid var(--line);
  display:grid;place-items:center;font-weight:700;font-size:13px}
.opt > div:last-child{min-width:0;overflow-wrap:anywhere}
.opt.sel{border-color:var(--brand);background:#1b2540}
.opt.ok{border-color:var(--ok);background:#12271c}
.opt.bad{border-color:var(--bad);background:#2a1216}
.navgrid{display:grid;grid-template-columns:repeat(auto-fill,minmax(40px,1fr));gap:6px;margin-top:14px}
.navgrid button{aspect-ratio:1;border-radius:8px;border:1px solid var(--line);background:var(--panel2);color:var(--ink);
  cursor:pointer;font-weight:600;font-size:13px}
.navgrid button.answered{background:#1b2540;border-color:#33508f}
.navgrid button.flagged{border-color:var(--warn)}
.navgrid button.cur{outline:2px solid var(--brand)}
.resbar{height:12px;border-radius:7px;background:var(--panel2);overflow:hidden;border:1px solid var(--line)}
.resbar > i{display:block;height:100%;background:linear-gradient(90deg,var(--brand),var(--brand2));transition:width .25s}
.score{font-size:44px;font-weight:800;line-height:1}
.pass{color:var(--ok)} .fail{color:var(--bad)}
.explain{border-left:3px solid var(--brand);background:var(--panel2);padding:12px 14px;border-radius:0 10px 10px 0;margin-top:12px;font-size:14.5px}
.tagrow{display:flex;gap:8px;flex-wrap:wrap;margin:6px 0 0;min-width:0}
.chip{background:var(--panel2);border:1px solid var(--line);border-radius:999px;padding:4px 11px;font-size:12.5px;color:var(--muted);
  display:inline-block;max-width:100%;overflow-wrap:anywhere;white-space:normal;word-break:break-word}
.hidden{display:none!important}
mark{background:#3a3410;color:#ffe58a;padding:0 2px;border-radius:3px}
.stamp{font-size:12px;color:var(--dim)}
.statusbar{display:flex;gap:10px;align-items:center;flex-wrap:wrap;margin-top:10px;color:var(--muted);font-size:14px}