:root{
  --bg:#080B11; --bg2:#0d1420; --card:rgba(255,255,255,.04); --bd:rgba(255,255,255,.09);
  --ink:#EAF0FB; --muted:#94A2BC; --faint:#62708C; --blue:#3F82F8; --blue-l:#62D8FF;
  --grad:linear-gradient(135deg,#62D8FF 0%,#3F82F8 50%,#2856D6 100%);
  --ok:#34d399; --bad:#f87171;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{background:var(--bg);color:var(--ink);font:16px/1.65 -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;-webkit-font-smoothing:antialiased}
a{color:var(--blue-l);text-decoration:none}
.wrap{max-width:1080px;margin:0 auto;padding:0 22px}
.grad-text{background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}
.muted{color:var(--muted)}

/* nav */
.nav{display:flex;align-items:center;justify-content:space-between;height:62px;border-bottom:1px solid var(--bd);position:sticky;top:0;background:rgba(8,11,17,.85);backdrop-filter:blur(10px);z-index:20}
.brand{display:flex;align-items:center;gap:9px;font-weight:800;font-size:18px}
.brand .logo{height:24px;width:auto;display:block}
.brand .dot{width:12px;height:12px;border-radius:50%;background:var(--grad)}
.nav .row{display:flex;align-items:center;gap:14px}

/* buttons */
.btn{display:inline-flex;align-items:center;gap:8px;font-weight:600;font-size:15px;padding:12px 20px;border-radius:11px;border:1px solid transparent;cursor:pointer;transition:.16s;text-align:center}
.btn-primary{background:var(--grad);color:#fff;box-shadow:0 8px 28px -10px rgba(63,130,248,.6)}
.btn-primary:hover{transform:translateY(-1px)}
.btn-ghost{border-color:var(--bd);color:var(--ink);background:var(--card)}
.btn-ghost:hover{border-color:var(--blue)}
.btn[disabled]{opacity:.45;cursor:not-allowed;transform:none}
.btn.sm{padding:8px 14px;font-size:13.5px}

/* hero / generic sections */
.hero{padding:76px 0 40px;text-align:center}
.hero h1{font-size:clamp(30px,5vw,50px);line-height:1.1;margin:0 0 18px;letter-spacing:-.02em}
.hero p.lede{font-size:clamp(16px,2.3vw,20px);color:var(--muted);max-width:640px;margin:0 auto 30px}
.cta-row{display:flex;gap:12px;justify-content:center;flex-wrap:wrap}
.eyebrow{font-size:12.5px;font-weight:700;letter-spacing:2px;text-transform:uppercase;color:var(--blue-l);margin-bottom:14px}
.card{background:var(--card);border:1px solid var(--bd);border-radius:16px;padding:22px}
.grid{display:grid;gap:16px}
.g3{grid-template-columns:repeat(3,1fr)}
.pill{display:inline-block;font-size:12px;padding:3px 10px;border-radius:99px;background:rgba(148,162,188,.14);color:var(--muted)}
.pill.done{background:rgba(52,211,153,.16);color:var(--ok)}

/* flow steps (landing "how it works") */
.flow{display:flex;gap:0;flex-wrap:wrap;margin-top:20px}
.fstep{flex:1 1 150px;min-width:140px;text-align:center;padding:0 8px}
.fnum{width:34px;height:34px;border-radius:50%;background:var(--grad);color:#fff;font-weight:700;display:flex;align-items:center;justify-content:center;margin:0 auto 10px}

/* catalog cards */
.course-card{display:block;text-decoration:none;color:inherit}
.course-card:hover{border-color:var(--blue)}
.course-card h3{margin:2px 0 4px;font-size:18px}
.progress{height:7px;border-radius:99px;background:rgba(255,255,255,.08);overflow:hidden;margin-top:14px}
.progress > i{display:block;height:100%;background:var(--grad)}

/* ── player ─────────────────────────────────────────────────────────── */
.player{display:grid;grid-template-columns:280px 1fr;min-height:calc(100vh - 62px)}
.rail{border-right:1px solid var(--bd);padding:22px 16px;overflow-y:auto}
.rail .ctitle{font-weight:700;font-size:14px;margin:0 0 4px}
.rail .cbar{height:6px;border-radius:99px;background:rgba(255,255,255,.08);overflow:hidden;margin:8px 0 18px}
.rail .cbar > i{display:block;height:100%;background:var(--grad)}
.mod{font-size:11px;font-weight:700;letter-spacing:1px;text-transform:uppercase;color:var(--faint);margin:16px 0 6px}
.snav{display:flex;align-items:center;gap:9px;padding:8px 10px;border-radius:9px;font-size:14px;color:var(--muted);cursor:pointer;border:1px solid transparent}
.snav:hover{background:var(--card)}
.snav.cur{background:rgba(63,130,248,.14);border-color:rgba(63,130,248,.4);color:var(--ink)}
.snav.locked{opacity:.5;cursor:not-allowed}
.snav .tick{width:18px;height:18px;border-radius:50%;border:1.5px solid var(--faint);display:flex;align-items:center;justify-content:center;font-size:11px;flex:0 0 auto}
.snav.done .tick{background:var(--ok);border-color:var(--ok);color:#04120c}
.snav.cur .tick{border-color:var(--blue-l)}

.stage{padding:40px 24px 120px;max-width:720px;margin:0 auto;width:100%}
.stage .kicker{color:var(--blue-l);font-size:13px;font-weight:700;letter-spacing:.4px;margin-bottom:6px}
.stage h1{font-size:clamp(24px,3.5vw,32px);line-height:1.2;margin:0 0 22px}
.lesson{font-size:16.5px;line-height:1.8}
.lesson h2{font-size:20px;margin:28px 0 10px}
.lesson h3{font-size:17px;margin:22px 0 8px}
.lesson p{color:#d7e0f2;margin:0 0 16px}
.lesson strong{color:#fff}
.lesson ul,.lesson ol{color:#d7e0f2;padding-left:22px;margin:0 0 16px}
.lesson li{margin:6px 0}
.lesson blockquote{border-left:3px solid var(--blue);margin:18px 0;padding:2px 0 2px 16px;color:var(--muted);font-style:italic}
.lesson code{background:rgba(255,255,255,.08);padding:2px 6px;border-radius:5px;font-size:14px}
.lesson table{width:100%;border-collapse:collapse;margin:16px 0;font-size:14.5px}
.lesson th,.lesson td{border:1px solid var(--bd);padding:9px 11px;text-align:left}
.lesson th{background:rgba(255,255,255,.04)}

/* quiz */
.q{margin:0 0 26px}
.q .qtext{font-weight:600;font-size:16.5px;margin-bottom:12px}
.opt{display:flex;align-items:flex-start;gap:11px;padding:13px 15px;border:1px solid var(--bd);border-radius:11px;margin-bottom:10px;cursor:pointer;transition:.14s}
.opt:hover{border-color:var(--blue)}
.opt.sel{border-color:var(--blue);background:rgba(63,130,248,.1)}
.opt.correct{border-color:var(--ok);background:rgba(52,211,153,.1)}
.opt.wrong{border-color:var(--bad);background:rgba(248,113,113,.1)}
.opt input{margin-top:3px}
.qresult{padding:16px 18px;border-radius:12px;margin:8px 0 20px;font-weight:600}
.qresult.pass{background:rgba(52,211,153,.12);color:var(--ok)}
.qresult.fail{background:rgba(248,113,113,.12);color:var(--bad)}

/* footer nav bar */
.stepbar{position:fixed;bottom:0;left:280px;right:0;background:rgba(8,11,17,.94);backdrop-filter:blur(10px);border-top:1px solid var(--bd);padding:14px 24px;display:flex;justify-content:space-between;align-items:center;gap:12px}
.stepbar .prog{font-size:13px;color:var(--muted)}

footer.foot{border-top:1px solid var(--bd);padding:26px 0;text-align:center;color:var(--faint);font-size:13px}

@media(max-width:820px){
  .g3{grid-template-columns:1fr}
  .player{grid-template-columns:1fr}
  .rail{display:none}
  .rail.open{display:block;position:fixed;inset:62px 0 0 0;z-index:15;background:var(--bg)}
  .stepbar{left:0}
  .stage{padding:26px 18px 110px}
}