:root{
--bg:#0b0d12;--ink:#e6e8ee;--muted:#8a90a0;--faint:#5c6270;
--panel:rgba(255,255,255,.035);--panel-2:rgba(255,255,255,.06);--line:rgba(255,255,255,.09);--line-2:rgba(255,255,255,.16);
--navy:#e9ecf5;--blue:#5b9bff;--good:#46d39a;--bad:#ff6b6b;--inset:#06070b;
--mono:"Fira Code",ui-monospace,monospace;--sans:"DM Sans",system-ui,sans-serif;--display:"DM Serif Display",Georgia,serif;}
*{box-sizing:border-box}
[hidden]{display:none!important}
html,body{background:var(--bg)}
body{margin:0;color:var(--ink);font-family:var(--sans);line-height:1.5;
  background:radial-gradient(1100px 520px at 50% -10%, rgba(91,155,255,.14), transparent 70%), var(--bg);
  background-attachment:fixed;min-height:100vh;-webkit-font-smoothing:antialiased}
a{color:var(--blue);text-decoration:none} a:hover{text-decoration:underline}

/* masthead */
.masthead{border-bottom:1px solid var(--line);padding:16px 28px;background:rgba(10,12,18,.6);backdrop-filter:blur(10px);position:sticky;top:0;z-index:20}
.mast-top{display:flex;flex-wrap:wrap;align-items:baseline;gap:14px}
.brand{font-family:var(--display);font-size:26px;color:#fff;letter-spacing:.2px}
.brand-sub{color:var(--blue)}
.tagline{color:var(--muted);font-size:15px;flex:1;min-width:220px}
.links{display:flex;gap:14px;align-items:center;font-size:14px}
.badge{background:rgba(240,200,90,.10);border:1px solid rgba(240,200,90,.35);color:#e7c66a;border-radius:20px;padding:3px 11px;font-size:12px}
.metrics{display:flex;flex-wrap:wrap;gap:8px;margin-top:13px}
.chip-m{font-family:var(--mono);font-size:12px;color:var(--ink);background:var(--panel);border:1px solid var(--line);border-radius:20px;padding:4px 12px}
.chip-m.count{color:#a7f0cf;border-color:rgba(70,211,154,.4);box-shadow:0 0 14px rgba(70,211,154,.18)}
.chip-m.streak{color:#ffb3b3;border-color:rgba(255,107,107,.35)}

/* layout */
main{display:grid;grid-template-columns:284px 1fr;gap:22px;max-width:1140px;margin:0 auto;padding:24px 28px 64px}
.rail{position:sticky;top:96px;align-self:start}
.search{width:100%;font-family:var(--sans);font-size:14px;color:var(--ink);background:var(--panel);border:1px solid var(--line);border-radius:11px;padding:9px 13px;margin-bottom:10px;outline:none}
.search::placeholder{color:var(--faint)} .search:focus{border-color:var(--line-2)}
.chips{display:flex;flex-wrap:wrap;gap:6px;margin-bottom:13px}
.chip{font-size:12px;border:1px solid var(--line);background:var(--panel);color:var(--muted);border-radius:16px;padding:4px 11px;cursor:pointer;text-transform:capitalize;transition:.15s}
.chip:hover{border-color:var(--line-2);color:var(--ink)}
.chip.active{background:var(--blue);border-color:var(--blue);color:#06121f;font-weight:600;box-shadow:0 0 14px rgba(91,155,255,.4)}
#scenario-list{list-style:none;margin:0;padding:0;display:flex;flex-direction:column;gap:9px}
.scn{border:1px solid var(--line);background:var(--panel);backdrop-filter:blur(6px);border-radius:13px;padding:11px 13px;cursor:pointer;transition:.16s}
.scn:hover{border-color:var(--line-2);background:var(--panel-2)}
.scn.active{border-color:var(--blue);box-shadow:0 0 0 1px var(--blue),0 0 22px rgba(91,155,255,.22)}
.scn-top{display:flex;align-items:center;gap:8px}
.dot{width:9px;height:9px;border-radius:50%;background:#3a4050;flex:none}
.dot.good{background:var(--good);box-shadow:0 0 9px rgba(70,211,154,.8)}
.dot.bad{background:var(--bad);box-shadow:0 0 9px rgba(255,107,107,.8)}
.scn .t{font-family:var(--mono);font-weight:500;color:#fff;flex:1}
.scn .cat{font-size:10px;letter-spacing:1px;text-transform:uppercase;color:var(--muted);background:rgba(255,255,255,.06);border:1px solid var(--line);border-radius:6px;padding:2px 6px}
.scn .b{font-size:12.5px;color:var(--muted);margin-top:4px}
.challenge-btn{width:100%;margin-top:14px;background:var(--panel);border:1px solid var(--line);border-radius:11px;padding:10px;font-weight:500;color:var(--ink);cursor:pointer;transition:.15s}
.challenge-btn:hover{border-color:var(--blue);color:var(--blue);box-shadow:0 0 16px rgba(91,155,255,.2)}
.rail-note{font-size:12.5px;color:var(--muted);margin-top:12px}

.stage{display:flex;flex-direction:column;gap:16px;min-width:0}
.panel{background:var(--panel);border:1px solid var(--line);border-radius:16px;padding:16px 18px;backdrop-filter:blur(10px);box-shadow:0 1px 0 rgba(255,255,255,.04) inset,0 18px 40px rgba(0,0,0,.25)}
.panel-h{font-size:13px;font-weight:700;color:#fff;margin-bottom:11px;display:flex;align-items:center;gap:8px}
.panel-hint{font-weight:400;color:var(--muted)}
.mono{font-family:var(--mono);font-size:13.5px}
.code{white-space:pre-wrap;word-break:break-word;margin:0}
.dim{color:var(--muted)}
/* JSON highlight (dark everywhere) */
.t-key{color:#7cc7ff} .t-str{color:#9ece6a} .t-num{color:#e0af68} .t-punct{color:#7c8190} .t-plain{color:#cfd2dc}

.toggle-row{display:flex;align-items:center;gap:12px;margin-bottom:10px}
.toggle-label{font-weight:500}
.switch{position:relative;display:inline-block;width:52px;height:28px}
.switch input{display:none}
.slider{position:absolute;inset:0;background:var(--good);border-radius:28px;transition:.15s;cursor:pointer;box-shadow:0 0 12px rgba(70,211,154,.45)}
.slider:before{content:"";position:absolute;height:22px;width:22px;left:3px;top:3px;background:#fff;border-radius:50%;transition:.15s}
input:checked + .slider{background:var(--bad);box-shadow:0 0 12px rgba(255,107,107,.45)}
input:checked + .slider:before{transform:translateX(24px)}

.ghost{margin-left:auto;background:none;border:1px solid var(--line);border-radius:8px;color:var(--blue);font-size:12px;padding:3px 10px;cursor:pointer}
.ghost:hover{border-color:var(--line-2)}
.editor{width:100%;height:200px;font-family:var(--mono);font-size:13px;color:var(--ink);background:var(--inset);border:1px solid var(--line);border-radius:10px;padding:12px;margin-top:10px;resize:vertical;outline:none}
.editor-note{font-size:12px;color:var(--muted);margin-top:8px}

.run-row{display:flex;align-items:center;gap:10px;flex-wrap:wrap}
.run{background:var(--blue);color:#04101f;border:none;border-radius:12px;font-size:16px;font-weight:700;padding:12px 24px;cursor:pointer;box-shadow:0 0 0 1px rgba(91,155,255,.5),0 10px 26px rgba(91,155,255,.35);transition:.15s}
.run:hover{filter:brightness(1.08);box-shadow:0 0 0 1px rgba(91,155,255,.7),0 12px 32px rgba(91,155,255,.5)}
.ctl{background:var(--panel);border:1px solid var(--line);border-radius:9px;color:var(--ink);font-size:13px;padding:7px 14px;cursor:pointer}
.ctl:hover{border-color:var(--blue);color:var(--blue)}

.console{background:var(--inset);border:1px solid var(--line);border-radius:12px;padding:16px 18px;font-family:var(--mono);font-size:13.5px;min-height:120px;color:#cfd2dc;box-shadow:0 0 30px rgba(91,155,255,.06) inset}
.stagerow{display:flex;gap:10px;padding:8px 0;border-bottom:1px solid rgba(255,255,255,.06)}
.stagerow:last-child{border-bottom:none}
.stagerow .glyph{flex:none;width:18px;text-align:center}
.stagerow .lbl{color:#9aa3b2;min-width:190px;flex:none}
.stagerow .body{white-space:pre-wrap;word-break:break-word;color:#cfd2dc}
.stagerow.good .glyph{color:var(--good);text-shadow:0 0 8px rgba(70,211,154,.6)}
.stagerow.bad .glyph{color:var(--bad);text-shadow:0 0 8px rgba(255,107,107,.6)}
.stagerow.verdict-good,.stagerow.verdict-bad{margin-top:6px;padding:12px 12px;border-radius:10px;border-bottom:none}
.stagerow.verdict-good{background:rgba(70,211,154,.08);border:1px solid rgba(70,211,154,.3)}
.stagerow.verdict-bad{background:rgba(255,107,107,.07);border:1px solid rgba(255,107,107,.3)}
.stagerow.verdict-good .body{color:#a7f0cf} .stagerow.verdict-bad .body{color:#ffd0d0}

.diff{display:grid;grid-template-columns:1fr 1fr;gap:14px}
.diff .col{border:1px solid var(--line);background:var(--panel);border-radius:12px;padding:13px 15px;font-size:13.5px}
.diff .col h4{margin:0 0 9px;font-size:13px}
.diff .without h4{color:var(--bad)} .diff .with h4{color:var(--good)}
.diff .step{margin:5px 0;color:var(--ink)}
.diff .reality{margin-top:9px;font-weight:600}
.diff .reality.broken{color:var(--bad)} .diff .reality.fixed{color:var(--good)}

.challenge-bar{display:flex;align-items:center;gap:10px;flex-wrap:wrap;background:var(--panel);border:1px solid var(--blue);border-radius:13px;padding:13px 16px;box-shadow:0 0 22px rgba(91,155,255,.18)}
.guess{background:var(--blue);color:#04101f;border:none;border-radius:9px;padding:8px 16px;font-weight:600;cursor:pointer}
.guess.next{background:rgba(255,255,255,.1);color:#fff}
.challenge-bar .ghost{margin-left:0}

.intro{position:fixed;inset:0;background:rgba(5,7,12,.66);backdrop-filter:blur(6px);display:flex;align-items:center;justify-content:center;padding:24px;z-index:50}
.intro-card{background:linear-gradient(180deg,rgba(30,36,52,.95),rgba(14,17,26,.96));border:1px solid var(--line-2);border-radius:20px;max-width:540px;padding:32px 34px;box-shadow:0 30px 80px rgba(0,0,0,.6)}
.intro-h{font-family:var(--display);font-size:32px;color:#fff;margin-bottom:14px}
.intro-card p{margin:0 0 14px;color:var(--ink)}
.intro-card code{background:rgba(255,255,255,.08);padding:1px 6px;border-radius:5px;font-family:var(--mono);font-size:.88em}
.intro-sub{color:var(--muted);font-size:14.5px}

@media (prefers-reduced-motion: no-preference){
  .stagerow{animation:fadein .35s ease both}
  .dot.good,.dot.bad{animation:pulse .4s ease}
  @keyframes fadein{from{opacity:0;transform:translateY(4px)}to{opacity:1;transform:none}}
  @keyframes pulse{0%{transform:scale(.6)}60%{transform:scale(1.3)}100%{transform:scale(1)}}
}
@media(max-width:800px){main{grid-template-columns:1fr}.rail{position:static}.diff{grid-template-columns:1fr}}