:root{
  --bg:#0a0d0c; --bg2:#0f1412; --card:#131a17; --card2:#18211d;
  --line:#243029; --line2:#2e3d35;
  --text:#e8f0eb; --muted:#93a89c; --dim:#6b8075;
  --accent:#5cf08c; --accent2:#2ee6a6; --accent-dim:#1f6b45;
  --blue:#5cc8f0; --amber:#f0c35c; --red:#f0705c;
  --mono:'JetBrains Mono',ui-monospace,SFMono-Regular,Menlo,monospace;
  --sans:'Inter',system-ui,-apple-system,Segoe UI,Roboto,sans-serif;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  background:radial-gradient(1200px 600px at 80% -10%,rgba(46,230,166,.10),transparent 60%),
             radial-gradient(900px 500px at -10% 10%,rgba(92,200,240,.07),transparent 55%),
             var(--bg);
  color:var(--text);font-family:var(--sans);line-height:1.55;min-height:100vh;
  -webkit-font-smoothing:antialiased;
}
a{color:var(--accent2);text-decoration:none}
a:hover{text-decoration:underline}

/* top bar */
.topbar{
  position:sticky;top:0;z-index:50;
  display:flex;flex-wrap:wrap;gap:18px;align-items:center;justify-content:space-between;
  padding:14px 28px;background:rgba(10,13,12,.82);backdrop-filter:blur(14px);
  border-bottom:1px solid var(--line);
}
.brand{display:flex;align-items:center;gap:14px;min-width:0}
.logo{
  width:44px;height:44px;border-radius:12px;flex:none;display:grid;place-items:center;
  background:linear-gradient(135deg,var(--accent),var(--accent2));
  color:#04120b;font-weight:800;letter-spacing:-1px;font-size:17px;
  box-shadow:0 0 26px rgba(92,240,140,.35);
}
.brand-text h1{font-size:16px;font-weight:700;letter-spacing:-.2px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.brand-text p{font-size:11.5px;color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.tabs{display:flex;gap:6px;flex-wrap:wrap}
.tab-btn{
  background:transparent;border:1px solid transparent;color:var(--muted);
  font:inherit;font-size:13px;font-weight:500;padding:8px 14px;border-radius:9px;cursor:pointer;
  transition:.18s;
}
.tab-btn:hover{color:var(--text);background:var(--card)}
.tab-btn.active{color:#04120b;background:var(--accent);font-weight:700}

main{max-width:1180px;margin:0 auto;padding:30px 24px 80px}
.panel{display:none;animation:fade .28s ease}
.panel.active{display:block}
@keyframes fade{from{opacity:0;transform:translateY(6px)}to{opacity:1;transform:none}}

/* hero */
.hero{display:grid;grid-template-columns:1.6fr 1fr;gap:26px;align-items:center;margin:8px 0 10px}
.pill{display:inline-block;font-size:11px;font-weight:600;letter-spacing:.6px;text-transform:uppercase;
  color:var(--accent2);background:rgba(46,230,166,.09);border:1px solid rgba(46,230,166,.25);
  padding:5px 11px;border-radius:99px;margin-bottom:16px}
.hero h2{font-size:clamp(26px,3.4vw,40px);line-height:1.12;letter-spacing:-1px;font-weight:800;margin-bottom:14px}
.lede{color:var(--muted);font-size:15.5px;max-width:60ch}
.hero-actions{display:flex;gap:10px;margin-top:22px;flex-wrap:wrap}
.hero-stats{display:grid;grid-template-columns:1fr 1fr;gap:10px}
.stat{background:linear-gradient(160deg,var(--card),var(--bg2));border:1px solid var(--line);
  border-radius:14px;padding:16px;text-align:center}
.stat b{display:block;font-size:26px;font-weight:800;color:var(--accent);letter-spacing:-1px}
.stat span{font-size:11.5px;color:var(--muted)}

.btn{font:inherit;font-size:13.5px;font-weight:600;padding:10px 18px;border-radius:10px;cursor:pointer;
  border:1px solid var(--line2);background:var(--card);color:var(--text);transition:.18s}
.btn:hover{background:var(--card2);border-color:var(--dim)}
.btn.primary{background:linear-gradient(135deg,var(--accent),var(--accent2));color:#04120b;border:none}
.btn.primary:hover{filter:brightness(1.06)}
.btn.ghost{background:transparent}

.section-title{font-size:12px;text-transform:uppercase;letter-spacing:1.4px;color:var(--dim);
  margin:38px 0 16px;font-weight:700}

.path{display:grid;grid-template-columns:repeat(auto-fit,minmax(180px,1fr));gap:12px}
.path-step{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:16px;position:relative;overflow:hidden}
.path-step .num{font-family:var(--mono);font-size:11px;color:var(--accent);opacity:.8}
.path-step h4{font-size:14.5px;margin:6px 0 6px}
.path-step p{font-size:12.5px;color:var(--muted);line-height:1.5}

.usecases{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:12px}
.uc{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:18px}
.uc h4{font-size:14px;margin-bottom:8px;color:var(--accent2)}
.uc p{font-size:13px;color:var(--muted)}

.callout{margin-top:26px;padding:18px 20px;border-left:3px solid var(--accent);
  background:linear-gradient(90deg,rgba(92,240,140,.07),transparent);border-radius:0 12px 12px 0;
  color:var(--muted);font-size:13.5px}
.callout b{color:var(--text)}

/* panel head */
.panel-head{display:flex;justify-content:space-between;align-items:flex-end;gap:16px;flex-wrap:wrap;margin-bottom:22px}
.panel-head h2{font-size:26px;letter-spacing:-.6px;font-weight:800}
.sub{color:var(--muted);font-size:13.5px;margin-top:4px}
kbd{font-family:var(--mono);font-size:11px;background:var(--card2);border:1px solid var(--line2);
  border-bottom-width:2px;border-radius:5px;padding:1px 6px;color:var(--text)}

/* flashcards */
.deck-chips{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:20px}
.chip{font:inherit;font-size:12.5px;font-weight:500;padding:8px 14px;border-radius:99px;cursor:pointer;
  background:var(--card);border:1px solid var(--line);color:var(--muted);transition:.16s}
.chip:hover{color:var(--text);border-color:var(--line2)}
.chip.active{background:rgba(92,240,140,.12);border-color:var(--accent-dim);color:var(--accent)}

.flash-wrap{perspective:1600px;max-width:760px;margin:0 auto}
.flashcard{height:320px;cursor:pointer;outline:none}
.fc-inner{position:relative;width:100%;height:100%;transition:transform .55s cubic-bezier(.4,.2,.2,1);transform-style:preserve-3d}
.flashcard.flipped .fc-inner{transform:rotateY(180deg)}
.fc-face{position:absolute;inset:0;backface-visibility:hidden;border-radius:20px;
  border:1px solid var(--line2);padding:30px;display:flex;flex-direction:column;justify-content:center;
  background:linear-gradient(160deg,var(--card2),var(--card));box-shadow:0 18px 50px rgba(0,0,0,.45)}
.fc-back{transform:rotateY(180deg);background:linear-gradient(160deg,#0f2a1e,#0c1a14);border-color:var(--accent-dim)}
.fc-label{font-size:10.5px;text-transform:uppercase;letter-spacing:1.6px;color:var(--dim);font-weight:700;margin-bottom:14px}
.fc-back .fc-label{color:var(--accent)}
.fc-face p{font-size:clamp(16px,2.1vw,21px);line-height:1.45;font-weight:500}
.fc-back p{font-size:clamp(14px,1.8vw,18px);color:#d6f5e4;line-height:1.55}

.fc-controls{display:flex;gap:10px;justify-content:center;margin:22px 0 14px;flex-wrap:wrap}
.fc-progress{max-width:760px;margin:0 auto;display:flex;align-items:center;gap:12px}
.bar{flex:1;height:6px;background:var(--card2);border-radius:99px;overflow:hidden}
.bar i{display:block;height:100%;width:0;background:linear-gradient(90deg,var(--accent),var(--accent2));transition:width .3s}
#fc-count{font-size:12px;color:var(--muted);font-family:var(--mono);white-space:nowrap}
.hint{text-align:center;color:var(--dim);font-size:11.5px;margin-top:14px}

/* labs */
.labs-list{display:flex;flex-direction:column;gap:12px}
.lab{background:var(--card);border:1px solid var(--line);border-radius:16px;overflow:hidden;transition:.18s}
.lab:hover{border-color:var(--line2)}
.lab-head{display:flex;align-items:center;gap:14px;padding:18px 20px;cursor:pointer;user-select:none}
.lab-head .idx{font-family:var(--mono);font-size:12px;color:var(--accent);background:rgba(92,240,140,.1);
  border:1px solid var(--accent-dim);padding:6px 10px;border-radius:8px;flex:none}
.lab-head h3{font-size:15.5px;font-weight:600;flex:1}
.lab-meta{display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.tag{font-size:10.5px;font-weight:600;letter-spacing:.4px;text-transform:uppercase;padding:4px 9px;border-radius:6px;
  background:var(--card2);color:var(--muted);border:1px solid var(--line2)}
.tag.multi{color:var(--blue)} .tag.low{color:var(--amber)} .tag.arista{color:var(--accent)}
.lab-body{display:none;padding:0 20px 24px;border-top:1px solid var(--line)}
.lab.open .lab-body{display:block;animation:fade .25s}
.lab-body h4{font-size:11px;text-transform:uppercase;letter-spacing:1.3px;color:var(--dim);margin:18px 0 8px}
.lab-body p{font-size:13.5px;color:var(--muted)}
.topo{font-family:var(--mono);font-size:12.5px;background:var(--bg2);border:1px solid var(--line);
  border-radius:10px;padding:14px;color:var(--accent2);white-space:pre-wrap;margin-top:4px}
.step{border:1px solid var(--line);border-radius:12px;margin:10px 0;overflow:hidden;background:var(--bg2)}
.step-head{display:flex;align-items:center;gap:10px;padding:11px 14px;background:var(--card2)}
.step-head .sn{font-family:var(--mono);font-size:11px;color:var(--accent);font-weight:600}
.step-head b{font-size:13px;font-weight:600}
.code{position:relative;background:#070b09;border-top:1px solid var(--line)}
.code pre{margin:0;padding:14px 14px;overflow:auto;font-family:var(--mono);font-size:12.5px;
  line-height:1.6;color:#cfe8da}
.copy{position:absolute;top:8px;right:8px;font:inherit;font-size:10.5px;font-weight:600;
  background:var(--card);border:1px solid var(--line2);color:var(--muted);padding:4px 9px;
  border-radius:6px;cursor:pointer}
.copy:hover{color:var(--accent);border-color:var(--accent-dim)}
.step-note{padding:9px 14px;font-size:12px;color:var(--dim);background:rgba(92,240,140,.03);border-top:1px dashed var(--line)}
.verify-list{margin:6px 0 0 0;padding-left:0;list-style:none}
.verify-list li{font-size:13px;color:var(--muted);padding:7px 0 7px 26px;position:relative;border-bottom:1px solid var(--line)}
.verify-list li:before{content:"✓";position:absolute;left:0;color:var(--accent);font-weight:700}
.challenge{margin-top:14px;padding:14px 16px;border-radius:10px;font-size:13px;
  background:rgba(240,195,92,.06);border:1px solid rgba(240,195,92,.25);color:#f0d9a8}
.challenge b{color:var(--amber)}

/* videos */
.video-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:14px}
.video-card{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:18px;
  display:flex;flex-direction:column;gap:8px;transition:.18s;text-decoration:none;color:inherit}
.video-card:hover{border-color:var(--accent-dim);transform:translateY(-2px);text-decoration:none}
.video-card .play{width:38px;height:38px;border-radius:10px;display:grid;place-items:center;
  background:rgba(92,240,140,.12);color:var(--accent);font-size:14px;margin-bottom:4px}
.video-card h4{font-size:14px;font-weight:600;line-height:1.35}
.video-card p{font-size:12.5px;color:var(--muted);flex:1}
.video-card .vc-tag{font-size:10.5px;text-transform:uppercase;letter-spacing:.5px;color:var(--accent2);font-weight:600}

/* sources */
.sources-list{display:flex;flex-direction:column;gap:26px}
.src-group h3{font-size:12px;text-transform:uppercase;letter-spacing:1.3px;color:var(--dim);margin-bottom:10px}
.src-group a{display:block;padding:12px 16px;background:var(--card);border:1px solid var(--line);
  border-radius:10px;margin-bottom:8px;font-size:13.5px;color:var(--text);transition:.16s}
.src-group a:hover{border-color:var(--accent-dim);background:var(--card2);text-decoration:none}
.src-group a span{color:var(--dim);font-size:11.5px;margin-left:8px}

footer{display:flex;justify-content:space-between;gap:16px;flex-wrap:wrap;
  border-top:1px solid var(--line);padding:20px 28px;color:var(--dim);font-size:11.5px;max-width:1180px;margin:0 auto}

@media (max-width:820px){
  .hero{grid-template-columns:1fr}
  .topbar{padding:12px 16px}
  main{padding:22px 16px 60px}
  .flashcard{height:360px}
  .lab-meta{display:none}
}