:root{
  --bg:#ffffff;--surface:#f8fafc;--text:#0f172a;--muted:#64748b;--border:#e2e8f0;
  --primary:#2563eb;--primary-fg:#ffffff;--accent:#0ea5e9;--success:#16a34a;
  --shadow:0 1px 2px rgba(0,0,0,.04),0 8px 24px rgba(15,23,42,.06);
  --radius:14px;--radius-sm:8px;
  --font:'Inter',system-ui,-apple-system,Segoe UI,Roboto,sans-serif;
}
[data-theme="dark"]{
  --bg:#0b1220;--surface:#121a2b;--text:#e5e7eb;--muted:#94a3b8;--border:#1f2a44;
  --primary:#60a5fa;--primary-fg:#0b1220;--accent:#22d3ee;
  --shadow:0 1px 2px rgba(0,0,0,.4),0 8px 24px rgba(0,0,0,.35);
}
*{box-sizing:border-box}
html,body{margin:0;padding:0;background:var(--bg);color:var(--text);font-family:var(--font);line-height:1.6;-webkit-font-smoothing:antialiased}
img{max-width:100%;display:block}
a{color:var(--primary);text-decoration:none}
a:hover{text-decoration:underline}
.container{max-width:1180px;margin:0 auto;padding:0 20px}
.site-header{position:sticky;top:0;z-index:50;background:var(--bg);border-bottom:1px solid var(--border);backdrop-filter:saturate(180%) blur(8px)}
.nav{display:flex;align-items:center;gap:16px;padding:14px 0;flex-wrap:wrap}
.brand{font-weight:800;font-size:20px;color:var(--text);letter-spacing:-0.02em}
.brand span{color:var(--primary)}
.nav-links{display:flex;gap:6px;flex-wrap:wrap;margin-left:auto;align-items:center}
.nav-links a{color:var(--text);padding:8px 12px;border-radius:8px;font-size:14px;font-weight:500}
.nav-links a:hover{background:var(--surface);text-decoration:none}
.nav-search{display:flex;align-items:center;gap:8px;background:var(--surface);padding:8px 12px;border-radius:10px;border:1px solid var(--border);min-width:220px}
.nav-search input{border:0;background:transparent;outline:none;color:var(--text);width:100%;font-size:14px}
.theme-toggle{background:var(--surface);border:1px solid var(--border);color:var(--text);padding:8px 10px;border-radius:8px;cursor:pointer;font-size:14px}
.hero{padding:64px 0 32px;text-align:center}
.hero h1{font-size:clamp(28px,4vw,46px);margin:0 0 12px;letter-spacing:-0.03em;font-weight:800}
.hero p{color:var(--muted);font-size:18px;max-width:680px;margin:0 auto}
.section{padding:36px 0}
.section h2{font-size:24px;margin:0 0 20px;letter-spacing:-0.02em}
.grid{display:grid;gap:16px;grid-template-columns:repeat(auto-fill,minmax(240px,1fr))}
.card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:20px;transition:transform .15s ease, box-shadow .15s ease;display:block;color:inherit}
.card:hover{transform:translateY(-2px);box-shadow:var(--shadow);text-decoration:none}
.card h3{margin:0 0 6px;font-size:16px;font-weight:700}
.card p{margin:0;color:var(--muted);font-size:14px}
.tag{display:inline-block;font-size:11px;font-weight:600;letter-spacing:.04em;text-transform:uppercase;color:var(--primary);background:color-mix(in oklab, var(--primary) 12%, transparent);padding:3px 8px;border-radius:999px;margin-bottom:8px}
.layout{display:grid;grid-template-columns:1fr 300px;gap:24px;align-items:start}
@media (max-width:960px){.layout{grid-template-columns:1fr}}
.tool{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:24px}
.tool h1{margin:0 0 6px;font-size:28px;letter-spacing:-0.02em}
.tool .lede{color:var(--muted);margin:0 0 20px}
.form-row{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-bottom:12px}
@media (max-width:560px){.form-row{grid-template-columns:1fr}}
label{display:block;font-size:13px;font-weight:600;color:var(--text);margin-bottom:6px}
input,select,textarea{width:100%;background:var(--bg);color:var(--text);border:1px solid var(--border);border-radius:var(--radius-sm);padding:10px 12px;font-size:15px;font-family:inherit;outline:none;transition:border-color .15s}
input:focus,select:focus,textarea:focus{border-color:var(--primary)}
.btn-row{display:flex;gap:8px;flex-wrap:wrap;margin-top:8px}
.btn{display:inline-flex;align-items:center;gap:6px;background:var(--primary);color:var(--primary-fg);border:0;border-radius:10px;padding:11px 16px;font-weight:600;font-size:14px;cursor:pointer;transition:opacity .15s}
.btn:hover{opacity:.92;text-decoration:none}
.btn.ghost{background:transparent;color:var(--text);border:1px solid var(--border)}
.result{margin-top:18px;background:var(--bg);border:1px solid var(--border);border-radius:var(--radius);padding:18px}
.result h3{margin:0 0 8px;font-size:14px;text-transform:uppercase;letter-spacing:.06em;color:var(--muted)}
.result .big{font-size:30px;font-weight:800;letter-spacing:-0.02em;color:var(--primary)}
.result .meta{font-size:13px;color:var(--muted);margin-top:6px}
.kv{display:grid;grid-template-columns:1fr auto;gap:6px 16px;margin-top:10px;font-size:14px}
.kv div:nth-child(odd){color:var(--muted)}
.kv div:nth-child(even){font-weight:600;text-align:right}
.ad{background:repeating-linear-gradient(45deg,var(--surface),var(--surface) 10px,var(--bg) 10px,var(--bg) 20px);border:1px dashed var(--border);border-radius:var(--radius);padding:24px;text-align:center;color:var(--muted);font-size:12px;letter-spacing:.08em;text-transform:uppercase;margin:24px 0}
.sidebar .ad{margin:0 0 16px}
.sidebar .card{margin-bottom:12px}
.faq{margin-top:24px}
.faq details{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-sm);padding:14px 16px;margin-bottom:8px}
.faq summary{cursor:pointer;font-weight:600}
.faq details p{color:var(--muted);margin:8px 0 0}
.formula{margin-top:20px;background:var(--bg);border:1px dashed var(--border);border-radius:var(--radius-sm);padding:14px 16px;font-family:ui-monospace,Menlo,monospace;font-size:13px;color:var(--text);overflow-x:auto}
.breadcrumb{font-size:13px;color:var(--muted);margin-bottom:14px}
.breadcrumb a{color:var(--muted)}
.footer{border-top:1px solid var(--border);margin-top:48px;background:var(--surface)}
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1fr 1fr;gap:24px;padding:36px 0}
@media (max-width:760px){.footer-grid{grid-template-columns:1fr 1fr}}
.footer h4{margin:0 0 10px;font-size:13px;text-transform:uppercase;letter-spacing:.08em;color:var(--muted)}
.footer ul{list-style:none;padding:0;margin:0}
.footer li{margin-bottom:6px;font-size:14px}
.footer a{color:var(--text)}
.copyright{text-align:center;padding:16px;border-top:1px solid var(--border);font-size:13px;color:var(--muted)}
.toast{position:fixed;bottom:24px;left:50%;transform:translateX(-50%);background:var(--text);color:var(--bg);padding:10px 18px;border-radius:999px;font-size:14px;opacity:0;pointer-events:none;transition:opacity .2s}
.toast.show{opacity:1}
.scientific-pad{display:grid;grid-template-columns:repeat(5,1fr);gap:6px;margin-top:12px}
.scientific-pad button{padding:12px;background:var(--bg);border:1px solid var(--border);border-radius:8px;cursor:pointer;color:var(--text);font-size:14px;font-weight:600}
.scientific-pad button.op{color:var(--primary)}
.scientific-pad button.eq{background:var(--primary);color:var(--primary-fg);border-color:var(--primary)}
.scientific-display{background:var(--bg);border:1px solid var(--border);border-radius:8px;padding:14px;text-align:right;font-family:ui-monospace,Menlo,monospace;font-size:22px;min-height:54px;word-break:break-all}
.search-results{position:absolute;top:100%;left:0;right:0;background:var(--bg);border:1px solid var(--border);border-radius:10px;margin-top:6px;box-shadow:var(--shadow);max-height:320px;overflow-y:auto;display:none;z-index:60}
.search-results.show{display:block}
.search-results a{display:block;padding:10px 12px;color:var(--text);font-size:14px;border-bottom:1px solid var(--border)}
.search-results a:last-child{border-bottom:0}
.search-results a:hover{background:var(--surface);text-decoration:none}
.nav-search-wrap{position:relative}