:root{
  --bg:#0a0e14; --bg2:#0f151e; --panel:#121a25; --line:#1f2a38;
  --text:#d7e0ea; --muted:#8a99ab; --accent:#22d3ee; --accent-ink:#04141a;
  --mono:"JetBrains Mono",ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  --sans:Inter,system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;
  --r:12px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--text);font:16px/1.6 var(--sans);
  background-image:
    linear-gradient(rgba(34,211,238,.06) 1px,transparent 1px),
    linear-gradient(90deg,rgba(34,211,238,.06) 1px,transparent 1px),
    linear-gradient(rgba(34,211,238,.025) 1px,transparent 1px),
    linear-gradient(90deg,rgba(34,211,238,.025) 1px,transparent 1px);
  background-size:100px 100px,100px 100px,20px 20px,20px 20px;}
a{color:var(--accent)}
h1,h2,h3{font-family:var(--mono);line-height:1.2;margin:0 0 .5em}
.wrap{max-width:1120px;margin:0 auto;padding:0 24px}
.skip{position:absolute;left:-999px;top:8px;background:var(--accent);color:var(--accent-ink);padding:8px 12px;border-radius:6px;z-index:100}
.skip:focus{left:8px}
:focus-visible{outline:2px solid var(--accent);outline-offset:3px}
.dim{color:var(--muted)}
.accent{color:var(--accent)}

/* nav */
.nav{position:sticky;top:0;z-index:20;background:rgba(10,14,20,.8);backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}
.nav-inner{display:flex;align-items:center;justify-content:space-between;height:64px;gap:12px}
.brand{display:flex;align-items:center;gap:10px;color:var(--text);text-decoration:none;font-family:var(--mono);font-weight:700}
.brand-mark{display:grid;place-items:center;width:34px;height:34px;border:1.5px solid var(--accent);border-radius:8px;color:var(--accent);font-size:15px}
.brand-mark sub{font-size:9px;vertical-align:-2px}
.brand-mark{display:flex;align-items:center;justify-content:center;gap:0}
.brand-name{letter-spacing:.02em}
.nav-links{display:flex;align-items:center;gap:8px;list-style:none;margin:0;padding:0}
.nav-links a:not(.btn){color:var(--muted);text-decoration:none;font-family:var(--mono);font-size:14px;padding:8px 10px}
.nav-links a:not(.btn):hover{color:var(--text)}

/* buttons */
.btn{display:inline-flex;align-items:center;justify-content:center;font-family:var(--mono);font-weight:600;font-size:14px;padding:9px 16px;border-radius:8px;text-decoration:none;border:1.5px solid transparent;transition:transform .15s,box-shadow .15s,background .15s;white-space:nowrap}
.btn-primary{background:var(--accent);color:var(--accent-ink)}
.btn-primary:hover{box-shadow:0 0 0 4px rgba(34,211,238,.18);transform:translateY(-1px)}
.btn-ghost{border-color:var(--line);color:var(--text);background:rgba(255,255,255,.02)}
.btn-ghost:hover{border-color:var(--accent);color:var(--accent)}
.btn-lg{padding:13px 22px;font-size:15px}
.btn-block{width:100%}

/* hero */
.hero{position:relative;overflow:hidden;border-bottom:1px solid var(--line);min-height:560px;display:flex;align-items:center}
#bulb{position:absolute;inset:0;width:100%;height:100%}
.hero::after{content:"";position:absolute;inset:0;background:linear-gradient(90deg,var(--bg) 0%,rgba(10,14,20,.85) 45%,rgba(10,14,20,.2) 100%);pointer-events:none}
.hero-inner{position:relative;z-index:1;width:100%;min-width:0;padding-top:72px;padding-bottom:72px}
.eyebrow{font-family:var(--mono);color:var(--accent);font-size:14px;margin:0 0 16px}
h1{font-size:clamp(32px,5vw,56px);max-width:20ch;letter-spacing:-.02em}
.lede{max-width:56ch;color:var(--muted);font-size:18px;margin:0 0 28px}
.hero-cta{display:flex;gap:12px;flex-wrap:wrap}
.hero-code{margin:36px 0 0;font-family:var(--mono);font-size:14px;color:var(--text);background:rgba(18,26,37,.75);border:1px solid var(--line);border-left:3px solid var(--accent);padding:12px 16px;border-radius:8px;display:inline-block;max-width:100%;overflow-x:auto}

/* sections */
.section{padding:88px 0}
h2{font-size:clamp(26px,3vw,34px)}
.hash{color:var(--accent);font-size:.6em;vertical-align:middle;margin-right:10px;border:1px solid var(--accent);border-radius:6px;padding:2px 7px}
.section-sub{color:var(--muted);margin:0 0 36px}

/* cards */
.cards{list-style:none;padding:0;margin:0;display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:20px}
.card{position:relative;display:flex;flex-direction:column;background:linear-gradient(180deg,var(--panel),var(--bg2));border:1px solid var(--line);border-radius:var(--r);padding:18px;transition:border-color .2s,transform .2s,box-shadow .2s}
.card:not(.card-soon):hover{border-color:rgba(34,211,238,.6);transform:translateY(-3px);box-shadow:0 12px 40px -12px rgba(34,211,238,.25)}
.card-fig{height:130px;border-radius:8px;background:#0b1119;border:1px solid var(--line);display:grid;place-items:center;margin-bottom:16px;overflow:hidden}
.card-fig svg{width:100%;height:100%;padding:8px}
.ground{stroke:var(--muted);stroke-width:1.2}
.hatch line{stroke:var(--muted);stroke-width:1}
.footing{fill:#33475e;stroke:var(--text);stroke-width:1}
.arrows line{stroke:var(--accent);stroke-width:1.5}
.bulbs path{fill:none;stroke:var(--accent);stroke-width:1.3}
.bulbs path:nth-child(2){opacity:.75}.bulbs path:nth-child(3){opacity:.5}.bulbs path:nth-child(4){opacity:.3}
.lbl{fill:var(--muted);font:9px var(--mono)}
.card-body{flex:1}
.card h3{font-size:20px;margin-bottom:6px}
.card p{color:var(--muted);font-size:14.5px;margin:0 0 12px}
.tags{list-style:none;padding:0;margin:0 0 16px;display:flex;gap:6px;flex-wrap:wrap}
.tags li{font:12px var(--mono);color:var(--accent);background:rgba(34,211,238,.08);border:1px solid rgba(34,211,238,.25);border-radius:999px;padding:2px 9px}
.card-btn{align-self:flex-start}
.card-soon{opacity:.55;border-style:dashed}
.card-fig-soon span{font:700 28px var(--mono);color:var(--line)}
.badge{align-self:flex-start;font:600 12px var(--mono);color:var(--muted);border:1px solid var(--line);border-radius:6px;padding:6px 10px}

/* pricing */
.plans{display:grid;grid-template-columns:repeat(2,minmax(0,360px));gap:20px}
.plan{position:relative;background:var(--panel);border:1px solid var(--line);border-radius:var(--r);padding:28px}
.plan-hl{border-color:var(--accent);box-shadow:0 0 0 1px var(--accent),0 20px 60px -20px rgba(34,211,238,.3)}
.plan h3{font-size:16px;color:var(--muted);font-weight:600}
.price{margin:8px 0 18px;font-family:var(--mono)}
.amt{font-size:44px;font-weight:700;color:var(--text)}
.per{color:var(--muted);margin-left:6px}
.feat{list-style:none;padding:0;margin:0 0 24px}
.feat li{padding:6px 0 6px 22px;position:relative;color:var(--text);font-size:15px}
.feat li::before{content:"▸";position:absolute;left:0;color:var(--accent)}
.ribbon{position:absolute;top:-12px;right:20px;background:var(--accent);color:var(--accent-ink);font:700 12px var(--mono);padding:4px 10px;border-radius:6px}

/* footer */
.footer{border-top:1px solid var(--line);padding:28px 0;font-size:13px;font-family:var(--mono)}
.footer-inner{display:flex;justify-content:space-between;gap:16px;flex-wrap:wrap}

/* mobile */
@media (max-width:720px){
  .nav-links li:not(:last-child):not(:nth-last-child(2)){display:none}
  .nav-links .btn{padding:7px 11px;font-size:13px}
  .brand-name{font-size:14px}
  .hero{min-height:0}
  .hero::after{background:linear-gradient(180deg,rgba(10,14,20,.55),rgba(10,14,20,.9))}
  .hero-inner{padding-top:48px;padding-bottom:48px}
  .lede{font-size:16px}
  .hero-code{font-size:12px;white-space:pre-wrap}
  .section{padding:60px 0}
  .plans{grid-template-columns:1fr}
}
@media (prefers-reduced-motion:reduce){*{transition:none!important;scroll-behavior:auto!important}}

/* applet placeholder page */
.placeholder{min-height:calc(100vh - 64px - 90px);display:grid;place-items:center;text-align:center;padding:48px 24px}
.placeholder p{color:var(--muted);max-width:52ch;margin:0 auto 24px}

/* free badge + disabled buttons */
.badge-free{display:inline-block;vertical-align:middle;margin-left:8px;font:700 11px var(--mono);letter-spacing:.04em;text-transform:uppercase;color:var(--accent-ink);background:var(--accent);border-radius:5px;padding:3px 7px}
.free-note{margin:0 0 22px;color:var(--text);font-size:15px}
.free-note .badge-free{margin:0 8px 0 0}
.free-note a{color:var(--accent)}
.btn[disabled],.btn[aria-disabled=true]{opacity:.45;cursor:not-allowed;transform:none!important;box-shadow:none!important}

/* footer columns (Learn / Applets) */
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1.4fr;gap:28px;padding-bottom:22px;margin-bottom:18px;border-bottom:1px solid var(--line)}
.footer-grid h2{font-size:12px;letter-spacing:.08em;text-transform:uppercase;color:var(--muted);margin:0 0 10px}
.footer-grid ul{list-style:none;margin:0;padding:0}
.footer-grid li{margin:0 0 8px}
.footer-grid a{color:var(--text);text-decoration:none}
.footer-grid a:hover{color:var(--accent);text-decoration:underline}
.footer-grid p{margin:8px 0 0;font-family:var(--sans);font-size:14px;max-width:38ch}
@media (max-width:720px){.footer-grid{grid-template-columns:1fr}}
.card-links{display:flex;gap:10px;align-items:center;flex-wrap:wrap;margin-top:auto}
.card-links .card-btn{margin-top:0}
.link-sm{font:600 13px var(--mono);color:var(--accent)}

/* article pages (/learn/) */
.article{max-width:780px;margin:0 auto;padding:48px 0 24px}
.article h1{font-size:clamp(30px,4.2vw,44px);margin:.2em 0 .5em}
.article h2{font-size:24px;margin:2.1em 0 .6em;padding-top:.4em;border-top:1px solid var(--line)}
.article h3{font-size:18px;margin:1.6em 0 .5em}
.article p,.article li{font-size:17px;line-height:1.75}
.article .lede{font-size:19px;color:var(--text)}
.article .meta{font:13px var(--mono);color:var(--muted)}
.article figure{margin:1.6em 0;text-align:center}
.article figure img{max-width:440px;width:100%;height:auto;background:#fff;border-radius:10px;padding:10px}
.article figcaption{font-size:14px;color:var(--muted);margin-top:.6em}
.article table{border-collapse:collapse;width:100%;margin:1em 0;font-size:15px}
.article th,.article td{border:1px solid var(--line);padding:8px 10px;text-align:left;vertical-align:top}
.article th{background:var(--panel);font-family:var(--mono);font-size:13px}
.article .toc{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:14px 20px;margin:1.5em 0}
.article .toc ol{margin:.4em 0 0;padding-left:1.3em}
.article .toc li{font-size:15px;line-height:1.7}
.eqbox{background:#0b1119;border:1px solid var(--line);border-left:3px solid var(--accent);border-radius:8px;padding:16px 18px;margin:1.1em 0;overflow-x:auto}
.eqbox math{font-size:1.25em;color:var(--text);font-family:"STIX Two Math","Cambria Math","Latin Modern Math","DejaVu Serif",Inter,serif}
.eqbox .eqlabel{display:block;font:600 12px var(--mono);color:var(--muted);margin-bottom:8px;text-transform:uppercase;letter-spacing:.06em}
.eqbox .plain{display:block;font:13px var(--mono);color:var(--muted);margin-top:10px}
.work{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:16px 20px;margin:1.2em 0}
.work h3{margin-top:0}
.work .ans{font:600 16px var(--mono);color:var(--accent)}
.cta-box{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:16px;background:linear-gradient(135deg,rgba(34,211,238,.12),rgba(34,211,238,.03));border:1px solid rgba(34,211,238,.5);border-radius:12px;padding:20px 22px;margin:2em 0}
.cta-box p{margin:0;font-size:16px}
.tribute{border-left:3px solid var(--muted);padding:6px 0 6px 16px;color:var(--muted);font-style:italic}
.refs li{font-size:15px;line-height:1.6;margin-bottom:.5em}
.about-app{max-width:900px}
.about-app ul{margin:.4em 0 0;padding-left:1.2em}
.about-app li{font-size:15px;color:var(--muted);line-height:1.6}
.eqbox math+math{margin-top:.7em}