/* © 2026 THOAI LE NEW — Premium Tech: navy, đen, cyan */
:root{
  --bg:#05070d; --navy:#0b1733; --navy2:#102248; --navy3:#16305f; --line:#1e3a6b;
  --cyan:#22d3ee; --blue:#3b82f6; --text:#e6f1ff; --muted:#8ea3c4;
  --amber:#fbbf24; --green:#34d399;
  --grad:linear-gradient(135deg,#22d3ee,#3b82f6);
  --glow:0 0 0 1px rgba(34,211,238,.35),0 10px 30px -10px rgba(34,211,238,.45);
  --depth:0 1px 0 rgba(255,255,255,.06) inset,0 12px 24px -12px rgba(0,0,0,.8),0 2px 4px rgba(0,0,0,.4);
  font-family:"Segoe UI",Arial,system-ui,sans-serif;
}
*{box-sizing:border-box}
body{margin:0;color:var(--text);line-height:1.6;font-size:16px;min-height:100vh;
  background:radial-gradient(1200px 600px at 10% -10%,#12306b 0,transparent 60%),radial-gradient(900px 500px at 110% 10%,#0c3a52 0,transparent 55%),var(--bg);
  -webkit-user-select:none;user-select:none;-webkit-touch-callout:none}
body::before{content:"";position:fixed;inset:0;pointer-events:none;opacity:.25;
  background-image:linear-gradient(rgba(34,211,238,.07) 1px,transparent 1px),linear-gradient(90deg,rgba(34,211,238,.07) 1px,transparent 1px);background-size:40px 40px}
a{color:var(--cyan)}
input{-webkit-user-select:text;user-select:text}

/* Thanh trên */
.top{position:sticky;top:0;z-index:30;display:flex;align-items:center;gap:16px;padding:10px 20px;background:rgba(5,7,13,.86);backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}
.brand{display:flex;align-items:baseline;gap:10px;text-decoration:none;white-space:nowrap}
.mark{font-weight:800;letter-spacing:.16em;background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}
.cn{color:var(--muted);font-weight:600;font-size:14px}
.search{flex:1;max-width:360px;margin-left:auto;display:flex;align-items:center;gap:8px;background:var(--navy);border:1px solid var(--line);border-radius:12px;padding:0 12px}
.search span{color:var(--muted)}
.search input{flex:1;min-width:0;background:none;border:0;color:var(--text);padding:9px 0;font:inherit;font-size:14.5px;outline:none}
.search:focus-within{box-shadow:var(--glow)}
.progress{display:flex;align-items:center;gap:8px;font-size:13.5px;color:var(--muted);white-space:nowrap}
.pbar{width:110px;height:8px;border-radius:9px;background:var(--navy2);overflow:hidden}
.pbar i{display:block;height:100%;width:0;background:var(--grad);transition:width .4s;box-shadow:0 0 12px var(--cyan)}

main{position:relative;max-width:1240px;margin:0 auto;padding:26px 20px 10px;min-height:70vh}
.kicker{color:var(--cyan);font-weight:700;font-size:12.5px;letter-spacing:.14em;text-transform:uppercase}
h1{font-size:clamp(24px,3.4vw,38px);line-height:1.18;margin:6px 0 14px}
.btn{display:inline-flex;align-items:center;gap:6px;border:0;cursor:pointer;border-radius:12px;padding:9px 16px;font:700 14px/1.2 inherit;font-family:inherit;text-decoration:none;color:#03121f;background:var(--grad);box-shadow:0 6px 18px -6px rgba(34,211,238,.6),inset 0 1px 0 rgba(255,255,255,.35);transition:transform .15s}
.btn:hover{transform:translateY(-1px)}
.btn.ghost{background:var(--navy);color:var(--text);border:1px solid var(--line);box-shadow:var(--depth)}
.btn.ghost:hover{border-color:var(--cyan)}
.btn.sm{padding:6px 12px;font-size:13px;border-radius:9px}
.tools{display:flex;flex-wrap:wrap;gap:10px}
.results{margin:16px 0 0;padding:12px 16px;border:1px solid var(--line);border-radius:12px;background:var(--navy);font-size:14.5px}
.results a{margin:0 4px;font-weight:700}

/* Mindmap */
.mm{position:relative;display:grid;grid-template-columns:230px 290px minmax(0,1fr);column-gap:64px;row-gap:14px;margin:30px 0 20px;padding:10px 0}
.links{position:absolute;inset:0;pointer-events:none;overflow:visible}
.links path{fill:none;stroke:url(#lg);stroke-width:2;opacity:.75}
.links path.l2{stroke-width:1.5;opacity:.45;stroke-dasharray:4 4}
.center{grid-column:1;grid-row:1 / span 20;align-self:center;position:relative;z-index:1;padding:26px 20px;border-radius:24px;text-align:center;
  background:linear-gradient(160deg,#16305f,#0b1733);border:1px solid rgba(34,211,238,.5);
  box-shadow:var(--glow),0 30px 60px -20px rgba(0,0,0,.9),inset 0 1px 0 rgba(255,255,255,.12);transform:perspective(900px) rotateY(8deg)}
.center span{display:block;font-weight:800;font-size:20px;letter-spacing:.04em;background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}
.center small{color:var(--muted)}
.row{display:contents}
.snode{grid-column:2;position:relative;z-index:1;display:flex;align-items:stretch;border-radius:16px;background:linear-gradient(160deg,var(--navy2),var(--navy));border:1px solid var(--line);box-shadow:var(--depth);transition:transform .2s,box-shadow .2s,border-color .2s;align-self:center}
.snode:hover{transform:perspective(700px) rotateX(5deg) translateY(-2px);box-shadow:var(--glow);border-color:var(--cyan)}
.sl{flex:1;padding:11px 14px;text-decoration:none;color:var(--text);min-width:0}
.sl b{display:block;font-size:11.5px;letter-spacing:.12em;color:var(--cyan)}
.sl span{font-weight:700;font-size:15px;line-height:1.3}
.tg{flex:none;width:40px;border:0;border-left:1px solid var(--line);background:transparent;color:var(--cyan);font-size:20px;cursor:pointer;border-radius:0 16px 16px 0}
.tg:hover{background:rgba(34,211,238,.1)}
.snode.done{border-color:var(--green)}
.snode.done .sl b{color:var(--green)}
.leaves{grid-column:3;position:relative;z-index:1;display:none;flex-wrap:wrap;gap:8px;align-self:center}
.row.open .leaves{display:flex}
.leaf{padding:6px 12px;border-radius:10px;background:rgba(11,23,51,.85);border:1px solid var(--line);color:var(--text);text-decoration:none;font-size:13.5px;transition:border-color .15s}
.leaf:hover{border-color:var(--cyan)}
.row.dim .snode,.row.dim .leaves{opacity:.3}
.row.hit .snode{box-shadow:var(--glow);border-color:var(--cyan)}
.intro{max-width:900px;margin:10px 0 0;padding:16px 20px;border-radius:16px;border:1px solid var(--line);background:rgba(11,23,51,.8);color:var(--text);font-size:15px}
.intro p{margin:6px 0}
.intro b{color:var(--cyan)}

/* Trang STEP */
.bar2{display:flex;justify-content:space-between;align-items:center;margin-bottom:16px}
.pos{color:var(--muted);font-weight:700;letter-spacing:.08em}
.stepv{max-width:900px;margin:0 auto}
.sh{display:flex;gap:18px;align-items:flex-start;padding:22px;border-radius:20px;background:linear-gradient(160deg,var(--navy2),var(--navy));border:1px solid var(--line);box-shadow:var(--depth);margin-bottom:16px}
.sh h1{margin:2px 0 10px}
.num{flex:none;width:62px;height:62px;border-radius:18px;display:grid;place-items:center;font-size:28px;font-weight:800;color:#03121f;background:var(--grad);box-shadow:0 10px 24px -8px rgba(34,211,238,.7),inset 0 2px 0 rgba(255,255,255,.4);transform:perspective(400px) rotateY(-10deg)}
.chips{display:flex;flex-wrap:wrap;gap:6px}
.chips span{font-size:13px;padding:3px 10px;border-radius:20px;background:rgba(34,211,238,.1);border:1px solid rgba(34,211,238,.3)}
details.part{margin-bottom:12px;border-radius:16px;background:rgba(11,23,51,.9);border:1px solid var(--line);box-shadow:var(--depth);overflow:hidden}
details.part>summary{cursor:pointer;list-style:none;display:flex;align-items:center;gap:12px;padding:14px 18px;font-weight:700;font-size:17px}
details.part>summary::-webkit-details-marker,details.sub>summary::-webkit-details-marker{display:none}
details.part>summary i{font-style:normal;width:28px;height:28px;border-radius:8px;display:grid;place-items:center;font-size:13px;background:var(--navy3);color:var(--cyan)}
details.part>summary::after{content:"▾";margin-left:auto;color:var(--muted);transition:transform .2s}
details.part:not([open])>summary::after{transform:rotate(-90deg)}
.pb{padding:0 20px 16px 58px}
.pb>p:first-child{margin-top:0}
ol.steps{padding-left:20px}
ol.steps li{margin:6px 0;padding-left:4px}
ol.steps li::marker{color:var(--cyan);font-weight:700}
details.sub{border:1px solid var(--line);border-radius:12px;margin:8px 0;background:var(--navy)}
details.sub summary{cursor:pointer;list-style:none;padding:10px 14px;font-weight:600;display:flex;gap:10px}
details.sub summary::before{content:"!";flex:none;width:22px;height:22px;border-radius:6px;display:grid;place-items:center;font-size:12px;background:rgba(251,191,36,.15);color:var(--amber)}
details.sub>div{padding:0 14px 10px 46px}
details.sub>div p{margin:4px 0 8px}
details.sub>div p b{color:var(--cyan)}
details.sub>div ol{margin:4px 0 8px;padding-left:20px}
details.sub>div li{margin:3px 0}
details.sub summary{font-size:15.5px}
.tag{display:inline-block;font-size:12px;font-weight:700;padding:2px 10px;border-radius:20px}
.tag.goc{background:rgba(34,211,238,.14);color:var(--cyan)}
.tag.ref{background:rgba(251,191,36,.14);color:var(--amber)}
.tag.bs{background:rgba(59,130,246,.18);color:#93c5fd}
.srcp{margin:10px 0 6px}
.warn,.todo{margin:10px 0;border-radius:12px;padding:10px 14px;font-size:15px}
.warn{border:1px solid rgba(251,191,36,.4);background:rgba(251,191,36,.07)}
.warn b{color:var(--amber)}
.todo{border:1px dashed rgba(251,191,36,.6);background:rgba(251,191,36,.05)}
.todo b{display:inline-block;margin-right:6px;font-size:11.5px;letter-spacing:.06em;text-transform:uppercase;color:#03121f;background:var(--amber);border-radius:6px;padding:1px 8px}
.pbox{margin:10px 0 14px;border-radius:12px;border:1px solid var(--line);background:#050b18;overflow:hidden}
.pbox .ph{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:8px 12px;border-bottom:1px solid var(--line);font-size:13px;color:var(--muted);font-weight:600}
.pbox pre{margin:0;padding:14px;white-space:pre-wrap;word-break:break-word;font:13.5px/1.55 Consolas,"Cascadia Mono",monospace;color:#cfe8ff;max-height:340px;overflow:auto}
.video{aspect-ratio:16/9;max-width:620px;display:grid;place-items:center;text-align:center;padding:16px;border-radius:14px;border:2px dashed var(--line);background:var(--navy);color:var(--muted)}
.video .play{font-size:30px;color:var(--cyan)}
.vwrap{aspect-ratio:16/9;max-width:720px;border-radius:14px;overflow:hidden}
.vwrap iframe,.vwrap video{width:100%;height:100%;border:0;display:block}
.check label{display:flex;gap:12px;align-items:flex-start;padding:10px 4px;border-bottom:1px solid var(--line);cursor:pointer}
.check label:last-child{border-bottom:0}
.check input{accent-color:var(--cyan);width:19px;height:19px;margin-top:3px;flex:none}
.check input:checked+span{color:var(--muted);text-decoration:line-through}
.donebar{text-align:center;margin:18px 0 6px}
.nav{max-width:900px;margin:18px auto 30px;display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap}

.foot{position:relative;max-width:1240px;margin:30px auto 0;padding:22px 20px 40px;border-top:1px solid var(--line);color:var(--muted);font-size:13.5px}
.toast{position:fixed;bottom:22px;left:50%;transform:translateX(-50%) translateY(100px);z-index:60;padding:10px 18px;border-radius:12px;font-weight:700;color:#03121f;background:var(--grad);transition:transform .25s}
.toast.show{transform:translateX(-50%) translateY(0)}

@media (max-width:1000px){.mm{grid-template-columns:200px 250px minmax(0,1fr);column-gap:44px}}
@media (max-width:820px){
  .mm{display:block;padding-left:0}
  .center{transform:none;margin-bottom:22px}
  .row{display:block;margin:0 0 14px 44px}
  .snode{margin-bottom:8px}
  .snode:hover{transform:none}
  .leaves{margin-left:36px;flex-direction:column;align-items:flex-start;gap:6px}
}
@media (max-width:640px){
  .top{flex-wrap:wrap;gap:8px 12px;padding:10px 14px}
  .cn{display:none}
  .search{order:3;flex-basis:100%;max-width:none}
  .progress{margin-left:auto}
  .pbar{width:70px}
  main{padding:18px 14px 6px}
  .row{margin-left:34px}
  .pb{padding:0 14px 14px}
  details.sub>div{padding-left:14px}
  .sh{padding:16px;gap:12px}.num{width:48px;height:48px;font-size:22px}
}
@media (prefers-reduced-motion:reduce){*{transition:none!important}}

/* Hướng làm A (Video → Video) / B (Hình → Video) */
[hidden]{display:none!important}
.tb{display:inline-block;flex:none;margin-right:8px;padding:1px 9px;border-radius:20px;font-size:11.5px;font-weight:800;letter-spacing:.04em;vertical-align:1px;white-space:nowrap}
.tb.tA{background:rgba(34,211,238,.16);color:var(--cyan);border:1px solid rgba(34,211,238,.45)}
.tb.tB{background:rgba(167,139,250,.16);color:#c4b5fd;border:1px solid rgba(167,139,250,.5)}
.tb.tC{background:rgba(142,163,196,.14);color:var(--muted);border:1px solid rgba(142,163,196,.4)}
details.sub.trk{border-left-width:4px}
details.sub.trk.tA{border-left-color:var(--cyan)}
details.sub.trk.tB{border-left-color:#a78bfa}
details.sub.trk.tC{border-left-color:var(--muted)}
details.sub.trk>summary{align-items:center}
details.sub.trk>summary::before{display:none}
details.sub.trk>div{padding-left:16px}
.trackbar{display:flex;flex-wrap:wrap;align-items:center;gap:8px;margin:16px 0 4px;padding:10px 12px;border-radius:14px;border:1px solid var(--line);background:rgba(11,23,51,.85)}
.trackbar>span{color:var(--muted);font-size:13.5px;font-weight:600;margin-right:4px}
.tbtn{border:1px solid var(--line);background:var(--navy);color:var(--text);border-radius:10px;padding:7px 12px;font:600 13.5px inherit;font-family:inherit;cursor:pointer}
.tbtn:hover{border-color:var(--cyan)}
.tbtn.on{background:var(--grad);color:#03121f;border-color:transparent}
.stepv>.trackbar{margin:0 0 14px}
.leaf.off{opacity:.3}
.leaf .tb{margin-right:6px}
.chips .tb{margin-right:4px}