:root{
  --indigo:#4f46e5; --indigo-dark:#4338ca; --indigo-soft:#eef2ff;
  --slate:#0f172a; --muted:#64748b; --line:#e2e8f0; --bg:#f8fafc;
  --card:#ffffff; --green:#059669; --radius:16px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Inter,Arial,sans-serif;
  color:var(--slate);background:var(--bg);line-height:1.6;font-size:16px}
a{color:var(--indigo);text-decoration:none}
a:hover{text-decoration:underline}
.wrap{max-width:1080px;margin:0 auto;padding:0 18px}
/* header */
.site-header{background:var(--card);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:50}
.site-header .wrap{display:flex;align-items:center;justify-content:space-between;min-height:64px}
.brand{font-weight:800;font-size:1.25rem;color:var(--slate);display:flex;align-items:center;gap:8px}
.brand .logo{width:30px;height:30px;border-radius:9px;background:linear-gradient(135deg,var(--indigo),#818cf8);
  display:inline-flex;align-items:center;justify-content:center;color:#fff;font-size:17px}
nav.main{display:flex;gap:4px;align-items:center}
nav.main a{color:var(--slate);font-weight:600;padding:8px 12px;border-radius:10px;font-size:.95rem}
nav.main a:hover{background:var(--indigo-soft);text-decoration:none;color:var(--indigo-dark)}
#navToggle{display:none;background:none;border:1px solid var(--line);border-radius:10px;font-size:1.3rem;
  padding:6px 12px;cursor:pointer;color:var(--slate)}
/* hero */
.hero{background:linear-gradient(135deg,#4f46e5 0%,#7c3aed 60%,#4338ca 100%);color:#fff;padding:56px 0 64px}
.hero h1{margin:0 0 12px;font-size:2.1rem;line-height:1.2;letter-spacing:-.02em}
.hero p.sub{opacity:.92;font-size:1.08rem;max-width:640px;margin:0 0 24px}
.hero-badges{display:flex;gap:10px;flex-wrap:wrap;font-size:.85rem}
.hero-badges span{background:rgba(255,255,255,.16);padding:6px 14px;border-radius:999px}
/* tool cards */
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:18px;margin:36px 0}
.tool-card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:24px;transition:transform .15s,box-shadow .15s}
.tool-card:hover{transform:translateY(-3px);box-shadow:0 12px 28px rgba(79,70,229,.12);text-decoration:none}
.tool-card .icon{font-size:2rem;margin-bottom:10px}
.tool-card h3{margin:0 0 8px;font-size:1.15rem;color:var(--slate)}
.tool-card p{margin:0;color:var(--muted);font-size:.94rem}
/* tool page layout */
.tool-hero{background:linear-gradient(135deg,#4f46e5,#7c3aed);color:#fff;padding:40px 0}
.tool-hero h1{margin:0 0 8px;font-size:1.8rem;letter-spacing:-.02em}
.tool-hero p{margin:0;opacity:.9;max-width:680px}
.calculator{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:26px;margin:-34px 0 30px;box-shadow:0 10px 30px rgba(15,23,42,.08);position:relative}
.field{margin-bottom:16px}
.field label{display:block;font-weight:700;margin-bottom:6px;font-size:.95rem}
.field input,.field select{width:100%;padding:12px 14px;border:1.5px solid var(--line);border-radius:12px;
  font-size:1rem;font-family:inherit}
.field input:focus,.field select:focus{outline:none;border-color:var(--indigo);box-shadow:0 0 0 3px var(--indigo-soft)}
.field-row{display:grid;grid-template-columns:1fr 1fr;gap:14px}
.btn{background:var(--indigo);color:#fff;border:none;border-radius:12px;padding:13px 26px;
  font-size:1rem;font-weight:700;cursor:pointer;width:100%}
.btn:hover{background:var(--indigo-dark)}
.btn-ghost{background:var(--indigo-soft);color:var(--indigo-dark)}
.result{background:#f0fdf4;border:1.5px solid #bbf7d0;border-radius:12px;padding:18px;margin-top:18px;display:none}
.result.show{display:block}
.result .big{font-size:1.9rem;font-weight:800;color:var(--green)}
.result .detail{color:var(--muted);font-size:.92rem;margin-top:6px}
.tabs{display:flex;gap:8px;margin-bottom:18px;flex-wrap:wrap}
.tabs button{border:1.5px solid var(--line);background:#fff;border-radius:999px;padding:9px 18px;
  font-weight:700;cursor:pointer;font-size:.92rem;color:var(--slate)}
.tabs button.active{background:var(--indigo);border-color:var(--indigo);color:#fff}
/* content sections */
.section{margin:40px 0}
.section h2{font-size:1.45rem;margin:0 0 14px;letter-spacing:-.01em}
.prose{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:26px}
.prose h3{margin:22px 0 8px;font-size:1.1rem}
.prose h3:first-child{margin-top:0}
.prose p,.prose li{color:#334155}
.faq details{border:1px solid var(--line);border-radius:12px;padding:14px 16px;margin-bottom:10px;background:#fff}
.faq summary{font-weight:700;cursor:pointer}
/* footer */
.site-footer{background:var(--slate);color:#cbd5e1;padding:40px 0;margin-top:60px}
.site-footer .wrap{display:grid;grid-template-columns:1.4fr 1fr 1fr;gap:28px}
.site-footer h4{color:#fff;margin:0 0 12px;font-size:1rem}
.site-footer a{color:#cbd5e1;display:block;margin-bottom:8px;font-size:.93rem}
.site-footer p{font-size:.9rem;margin:0 0 10px}
.bottom-bar{border-top:1px solid #1e293b;margin-top:28px;padding-top:18px;font-size:.85rem;color:#94a3b8}
/* breadcrumbs */
.crumbs{font-size:.85rem;color:var(--muted);margin:18px 0 0}
.crumbs a{color:var(--muted)}
@media(max-width:760px){
  nav.main{display:none;position:absolute;top:64px;left:0;right:0;background:#fff;
    flex-direction:column;align-items:stretch;padding:10px 18px 18px;border-bottom:1px solid var(--line)}
  nav.main.open{display:flex}
  nav.main a{padding:12px}
  #navToggle{display:block}
  .hero h1{font-size:1.65rem}
  .field-row{grid-template-columns:1fr}
  .site-footer .wrap{grid-template-columns:1fr}
  .calculator{margin-top:-24px;padding:20px}
}