*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
:root{
  --bg:#ffffff;--bg-alt:#f7f8fa;--text:#1a1a2e;--text-muted:#5a6072;
  --primary:#1a56db;--primary-hover:#1141b0;--border:#e2e5ea;
  --radius:8px;--max-w:900px;--font:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,sans-serif;
  --accent:#e8f0fe;--green:#059669;--green-bg:#ecfdf5;--orange:#d97706;--orange-bg:#fffbeb;
}
html{font-size:16px;-webkit-text-size-adjust:100%}
body{font-family:var(--font);color:var(--text);background:var(--bg);line-height:1.6}
a{color:var(--primary);text-decoration:none}a:hover{text-decoration:underline;color:var(--primary-hover)}
.wrap{max-width:var(--max-w);margin:0 auto;padding:0 1rem}
header{background:var(--bg);border-bottom:1px solid var(--border);padding:.75rem 0}
header .wrap{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:.5rem}
.logo{font-size:1.25rem;font-weight:700;color:var(--text);text-decoration:none}.logo span{color:var(--primary)}
nav a{color:var(--text-muted);font-size:.875rem;margin-left:1.25rem}nav a:hover{color:var(--primary)}
main{padding:1.5rem 0 3rem}
footer{background:var(--bg-alt);border-top:1px solid var(--border);padding:1.5rem 0;font-size:.8rem;color:var(--text-muted)}
footer .wrap{display:flex;justify-content:space-between;flex-wrap:wrap;gap:.5rem}
footer a{color:var(--text-muted)}

.breadcrumbs{font-size:.8rem;color:var(--text-muted);margin-bottom:1.25rem;list-style:none;display:flex;flex-wrap:wrap;gap:.25rem}
.breadcrumbs li::after{content:"›";margin-left:.35rem;color:var(--border)}
.breadcrumbs li:last-child::after{content:""}
.breadcrumbs a{color:var(--text-muted)}

h1{font-size:1.65rem;font-weight:700;margin-bottom:.4rem;line-height:1.25}
h2{font-size:1.2rem;font-weight:600;margin:1.75rem 0 .75rem}
h3{font-size:1rem;font-weight:600;margin:1.25rem 0 .5rem}
.subtitle{color:var(--text-muted);font-size:.95rem;margin-bottom:1.25rem}

/* Calculator */
.calc{background:var(--bg-alt);border:1px solid var(--border);border-radius:var(--radius);padding:1.5rem;margin-bottom:1.5rem}
.calc-row{display:flex;align-items:center;gap:.75rem;margin-bottom:.75rem;flex-wrap:wrap}
.calc label{font-size:.8rem;font-weight:600;color:var(--text-muted);text-transform:uppercase;letter-spacing:.03em;min-width:50px}
.calc input{flex:1;min-width:120px;padding:.6rem .75rem;font-size:1.1rem;border:2px solid var(--border);border-radius:var(--radius);font-family:var(--font);transition:border-color .15s}
.calc input:focus{outline:none;border-color:var(--primary)}
.calc-unit{font-size:.9rem;color:var(--text-muted);min-width:40px}
.calc-result{background:var(--green-bg);border:1px solid #a7f3d0;border-radius:var(--radius);padding:.75rem 1rem;font-size:1.1rem;font-weight:600;color:var(--green);margin-top:.5rem;min-height:2.8rem;display:flex;align-items:center}
.calc-btns{display:flex;gap:.5rem;margin-top:.75rem;flex-wrap:wrap}
.btn{padding:.5rem 1rem;font-size:.85rem;border:1px solid var(--border);border-radius:var(--radius);background:var(--bg);color:var(--text);cursor:pointer;font-family:var(--font);transition:all .15s}
.btn:hover{border-color:var(--primary);color:var(--primary)}
.btn-swap{background:var(--accent);border-color:var(--primary);color:var(--primary)}

/* Formula box */
.formula-box{background:var(--orange-bg);border:1px solid #fde68a;border-radius:var(--radius);padding:1rem 1.25rem;margin-bottom:1.5rem;font-size:.95rem}
.formula-box code{font-size:1.05rem;font-weight:600;color:var(--orange);font-family:monospace}

/* Data table */
.data-table{width:100%;border-collapse:collapse;margin-bottom:1.5rem;font-size:.9rem}
.data-table th{text-align:left;padding:.55rem .75rem;background:var(--bg-alt);border-bottom:2px solid var(--border);font-weight:600;color:var(--text-muted);font-size:.8rem;text-transform:uppercase;letter-spacing:.03em}
.data-table td{padding:.55rem .75rem;border-bottom:1px solid var(--border);font-variant-numeric:tabular-nums}
.data-table tr:last-child td{border-bottom:none}
.data-table td:first-child{font-weight:500}

/* Link grid */
.link-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:.5rem;margin-bottom:1.5rem}
.link-grid a{display:block;padding:.55rem .75rem;background:var(--bg-alt);border-radius:var(--radius);font-size:.875rem;border:1px solid var(--border);transition:border-color .15s}
.link-grid a:hover{border-color:var(--primary);text-decoration:none}

/* Category cards */
.cat-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:.75rem;margin-bottom:1.5rem}
.cat-card{display:block;padding:1rem 1.25rem;background:var(--bg);border:1px solid var(--border);border-radius:var(--radius);transition:border-color .15s,box-shadow .15s}
.cat-card:hover{border-color:var(--primary);box-shadow:0 2px 8px rgba(26,86,219,.08);text-decoration:none}
.cat-card .icon{font-size:1.5rem;margin-bottom:.35rem}
.cat-card strong{display:block;font-size:1rem;color:var(--text)}
.cat-card span{font-size:.8rem;color:var(--text-muted)}

.prose{margin-bottom:1.5rem;font-size:.93rem;line-height:1.7;color:var(--text)}.prose p{margin-bottom:.75rem}
.ad-slot{text-align:center;margin:1.5rem 0;min-height:90px}
.ad-slot-inline{margin:1rem 0}

.two-col{display:block}
@media(min-width:768px){.two-col{display:grid;grid-template-columns:1fr 280px;gap:1.5rem}}

@media(max-width:600px){
  h1{font-size:1.3rem}
  .calc{padding:1rem}
  .link-grid{grid-template-columns:1fr 1fr}
  .cat-grid{grid-template-columns:1fr}
  header .wrap{flex-direction:column;align-items:flex-start}
  nav{margin-top:.25rem}nav a{margin-left:0;margin-right:1rem}
}