/* Phyxics Virtual Lab — shared design kit */
:root{
  --bg:#f5f7fb; --card:#ffffff; --ink:#152033; --muted:#5b6880; --line:#dde3ee; --grid:#e9eef6;
  --brand:#2457d6; --brand-ink:#ffffff; --accent:#e8590c; --good:#2b8a3e; --bad:#c92a2a;
  --curve:#2457d6; --curve2:#7048e8; --area:rgba(36,87,214,.18); --area-neg:rgba(201,42,42,.18);
  --rect:rgba(232,89,12,.22); --rect-line:#e8590c; --radius:14px;
  --shadow:0 1px 2px rgba(16,24,40,.06),0 4px 16px rgba(16,24,40,.06);
  font-family:system-ui,-apple-system,"Segoe UI",Roboto,Ubuntu,"Helvetica Neue",Arial,sans-serif;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){
  :root{
    --bg:#0f141c; --card:#171e29; --ink:#e7ecf4; --muted:#9aa7bd; --line:#2a3443; --grid:#202a38;
    --brand:#5b8cff; --accent:#ff922b; --good:#51cf66; --bad:#ff6b6b;
    --curve:#74a0ff; --curve2:#b197fc; --area:rgba(116,160,255,.22); --area-neg:rgba(255,107,107,.22);
    --rect:rgba(255,146,43,.22); --rect-line:#ff922b;
    --shadow:0 1px 2px rgba(0,0,0,.3),0 4px 16px rgba(0,0,0,.25); color-scheme:dark;
  }
}
*{box-sizing:border-box}
html,body{margin:0;background:var(--bg);color:var(--ink)}
body{line-height:1.5;font-size:16px}
a{color:var(--brand)}
.wrap{max-width:1180px;margin:0 auto;padding:0 16px}
header.top{background:var(--card);border-bottom:1px solid var(--line)}
header.top .wrap{display:flex;align-items:center;gap:12px;min-height:60px;flex-wrap:wrap}
.logo{font-weight:800;font-size:19px;color:var(--ink);text-decoration:none;letter-spacing:-.01em}
.logo span{color:var(--brand)}
.crumb{color:var(--muted);font-size:14px}
.crumb a{color:var(--muted);text-decoration:none}
.crumb a:hover{color:var(--brand)}
.spacer{flex:1}
h1{font-size:clamp(24px,3.4vw,34px);line-height:1.15;margin:22px 0 6px;letter-spacing:-.02em}
h2{font-size:20px;margin:0 0 10px}
h3{font-size:16px;margin:0 0 6px}
.lead{color:var(--muted);margin:0 0 18px;max-width:760px}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);padding:16px}
.grid2{display:grid;grid-template-columns:minmax(0,1.6fr) minmax(0,1fr);gap:16px}
@media (max-width:860px){.grid2{grid-template-columns:1fr}}
.stack{display:flex;flex-direction:column;gap:16px}
canvas{display:block;width:100%;touch-action:none}
.plot{height:380px}
.plot.small{height:220px}
.visual{height:240px}
@media (max-width:600px){.plot{height:300px}.visual{height:210px}}

/* tabs / pills */
.tabs{display:inline-flex;background:var(--grid);border-radius:999px;padding:4px;gap:2px;flex-wrap:wrap}
.tabs button{border:0;background:transparent;color:var(--muted);font:inherit;font-weight:600;font-size:14px;padding:7px 14px;border-radius:999px;cursor:pointer}
.tabs button[aria-pressed="true"]{background:var(--card);color:var(--brand);box-shadow:var(--shadow)}
.controls{display:flex;flex-wrap:wrap;gap:14px 20px;align-items:end;margin-top:14px}
.ctl{display:flex;flex-direction:column;gap:4px;min-width:170px;flex:1}
.ctl label{font-size:13px;color:var(--muted);font-weight:600}
.ctl output{font-variant-numeric:tabular-nums;color:var(--ink);font-weight:600}
select,input[type=range]{font:inherit}
select{padding:8px 10px;border-radius:10px;border:1px solid var(--line);background:var(--card);color:var(--ink)}
input[type=range]{width:100%;accent-color:var(--brand)}
.btn{border:0;border-radius:10px;padding:9px 16px;font:inherit;font-weight:700;cursor:pointer;background:var(--brand);color:var(--brand-ink)}
.btn.ghost{background:var(--grid);color:var(--ink)}
.check{display:flex;align-items:center;gap:8px;font-size:14px;color:var(--ink);cursor:pointer}

/* readouts */
.readouts{display:grid;grid-template-columns:repeat(auto-fit,minmax(130px,1fr));gap:10px;margin-top:12px}
.ro{background:var(--grid);border-radius:10px;padding:10px 12px}
.ro small{display:block;color:var(--muted);font-size:12px;font-weight:600;text-transform:uppercase;letter-spacing:.04em}
.ro b{font-size:20px;font-variant-numeric:tabular-nums}
.say{margin:12px 0 0;padding:12px 14px;border-left:4px solid var(--accent);background:var(--grid);border-radius:0 10px 10px 0}
.formula{font-family:"Cambria Math","STIX Two Math","Times New Roman",serif;font-size:18px}
.explain p{margin:0 0 10px}
.explain ul{margin:6px 0 0;padding-left:20px}
.hidden{display:none!important}
footer{color:var(--muted);font-size:13px;padding:30px 0 40px;text-align:center}

/* portal */
.hero{padding:26px 0 8px}
.levels{margin:6px 0 22px}
.section{margin:0 0 28px}
.section-head{display:flex;align-items:baseline;gap:10px;flex-wrap:wrap;margin-bottom:10px}
.section-head p{margin:0;color:var(--muted);font-size:14px}
.tools{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:12px}
.tool{display:flex;flex-direction:column;gap:6px;text-decoration:none;color:var(--ink);transition:transform .12s,border-color .12s}
a.tool:hover{transform:translateY(-2px);border-color:var(--brand)}
.tool .icon{font-size:26px;line-height:1}
.tool p{margin:0;color:var(--muted);font-size:14px}
.tags{display:flex;gap:6px;flex-wrap:wrap;margin-top:auto;padding-top:6px}
.tag{font-size:11px;font-weight:700;padding:3px 8px;border-radius:999px;background:var(--grid);color:var(--muted)}
.tag.live{background:rgba(43,138,62,.15);color:var(--good)}
.tool.soon{opacity:.62}