:root {
  --bg: #0f172a;
  --card: #111827;
  --card-2: #1f2937;
  --text: #e5e7eb;
  --muted: #b6c2d9;
  --accent: #38bdf8;
  --ok: #22c55e;
  --border: #334155;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: Inter, Segoe UI, system-ui, -apple-system, sans-serif;
  background: linear-gradient(180deg, #020617 0%, #0b1020 100%);
  color: var(--text);
}
.wrap { max-width: 1100px; margin: 0 auto; padding: 1rem; }
.site-header { border-bottom: 1px solid var(--border); background: rgba(2, 6, 23, 0.8); }
.site-header h1 { margin-bottom: 0.25rem; }
.site-header p, .intro p { color: var(--muted); }
.card {
  background: rgba(17,24,39,0.85);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 0.9rem;
  margin: 0.85rem 0;
  backdrop-filter: blur(4px);
}
#search {
  width: 100%;
  border: 1px solid var(--border);
  background: #0b1220;
  color: var(--text);
  border-radius: 10px;
  padding: 0.65rem 0.8rem;
}
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1rem;
}
.calc-title { margin: 0 0 0.25rem 0; }
.calc-description { color: var(--muted); margin-top: 0; }
.calc-form { display: grid; gap: 0.6rem; margin: 0.75rem 0; }
.calc-form label { font-size: 0.9rem; color: var(--muted); }
.calc-form .field { display: grid; gap: 0.25rem; }
.calc-form input, .calc-form select {
  width: 100%;
  border: 1px solid var(--border);
  background: #0b1220;
  color: var(--text);
  border-radius: 8px;
  padding: 0.5rem 0.65rem;
}
.result {
  border: 1px dashed #1e293b;
  background: #0b1220;
  border-radius: 10px;
  padding: 0.75rem;
}
.result h4 { margin: 0 0 0.5rem 0; font-size: 0.92rem; color: var(--muted); }
.result-value { font-size: 1.2rem; font-weight: 700; color: var(--ok); }
.result-meta { margin: 0.35rem 0 0; color: var(--muted); font-size: 0.85rem; }
summary { cursor: pointer; color: var(--accent); margin-top: 0.65rem; }
.formula .katex-display { margin: 0.6rem 0 0.4rem; overflow-x: auto; overflow-y: hidden; }
.formula-vars { margin: 0.5rem 0 0; padding-left: 1.1rem; }
.formula-vars li { margin: 0.35rem 0; color: var(--muted); }
.formula-vars strong { color: var(--text); font-weight: 600; }
.site-footer { border-top: 1px solid var(--border); margin-top: 2rem; color: var(--muted); }
.hidden { display: none; }
.ad-slot { text-align: center; color: var(--muted); border-style: dashed; min-height: 120px; display: grid; align-content: start; padding-top: 0.75rem; }
.cta-button {
  display: inline-block;
  margin-top: 0.35rem;
  border: 1px solid var(--accent);
  background: rgba(56,189,248,0.12);
  color: #d8f3ff;
  border-radius: 8px;
  padding: 0.4rem 0.65rem;
  font-size: 0.86rem;
  text-decoration: none;
}
.cta-button:hover { text-decoration: none; background: rgba(56,189,248,0.2); }
@media (max-width: 640px) {
  .wrap { padding: 0.7rem; }
  .card { padding: 0.75rem; margin: 0.65rem 0; }
  .grid { gap: 0.7rem; }
  .calc-form { gap: 0.5rem; }
  .ad-slot { min-height: 74px; padding-top: 0.5rem; }
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }