:root {
  --bg: #f7f8fa;
  --surface: #ffffff;
  --text: #1c2430;
  --muted: #5b6676;
  --border: #e2e6ec;
  --accent: #2563eb;
  --accent-soft: #e8efff;
  --result: #0f7a4a;
  --radius: 12px;
  --max: 1080px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #11151c;
    --surface: #1a2029;
    --text: #e6eaf0;
    --muted: #9aa5b4;
    --border: #2b3340;
    --accent: #6c9bff;
    --accent-soft: #1f2b44;
    --result: #4ade9a;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 17px/1.65 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
a { color: var(--accent); }
img { max-width: 100%; }

.wrap { max-width: var(--max); margin: 0 auto; padding: 0 16px; }

/* Cabecera */
.site-header { background: var(--surface); border-bottom: 1px solid var(--border); }
.site-header .wrap { display: flex; align-items: center; justify-content: space-between; gap: 16px; min-height: 64px; flex-wrap: wrap; }
.logo { font-weight: 800; font-size: 1.25rem; color: var(--text); text-decoration: none; letter-spacing: -0.02em; }
.logo span { color: var(--accent); }
.nav { display: flex; gap: 18px; flex-wrap: wrap; font-size: 0.95rem; }
.nav a { color: var(--muted); text-decoration: none; }
.nav a:hover { color: var(--accent); }

/* Contenido */
main { padding: 32px 0 56px; }
h1 { font-size: clamp(1.7rem, 4vw, 2.4rem); line-height: 1.2; margin: 0 0 12px; letter-spacing: -0.02em; }
h2 { font-size: 1.4rem; margin: 40px 0 12px; }
h3 { font-size: 1.1rem; margin: 24px 0 8px; }
.lead { color: var(--muted); font-size: 1.1rem; margin: 0 0 28px; max-width: 70ch; }
.breadcrumb { font-size: 0.9rem; color: var(--muted); margin-bottom: 16px; }
.breadcrumb a { color: var(--muted); }
article { max-width: 760px; }

/* Rejilla de calculadoras */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 16px; }
.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px; text-decoration: none; color: var(--text); display: block;
  transition: border-color .15s, transform .15s;
}
.card:hover { border-color: var(--accent); transform: translateY(-2px); }
.card h2, .card h3 { margin: 0 0 6px; font-size: 1.15rem; }
.card p { margin: 0; color: var(--muted); font-size: 0.95rem; }
.card .icon { font-size: 1.6rem; margin-bottom: 8px; display: block; }

/* Calculadora */
.calc {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 24px; margin: 8px 0 32px; max-width: 760px;
}
.fields { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 16px; }
label { display: block; font-weight: 600; font-size: 0.95rem; margin-bottom: 6px; }
input, select {
  width: 100%; padding: 12px 14px; font: inherit; color: var(--text);
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
}
input:focus, select:focus { outline: 2px solid var(--accent); outline-offset: 1px; border-color: transparent; }
button {
  margin-top: 20px; padding: 12px 22px; font: inherit; font-weight: 700;
  background: var(--accent); color: #fff; border: 0; border-radius: 8px; cursor: pointer;
}
button:hover { filter: brightness(1.08); }
.result {
  margin-top: 20px; padding: 16px 18px; border-radius: 8px; background: var(--accent-soft);
  font-size: 1.05rem; display: none;
}
.result.show { display: block; }
.result strong { color: var(--result); font-size: 1.35rem; }
.result.error strong { color: #d63b3b; }
.tabs { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 18px; }
.tabs button { margin: 0; background: var(--bg); color: var(--text); border: 1px solid var(--border); font-weight: 600; padding: 8px 14px; }
.tabs button.active { background: var(--accent); color: #fff; border-color: var(--accent); }
.panel { display: none; }
.panel.active { display: block; }

table { width: 100%; border-collapse: collapse; margin: 16px 0; font-size: 0.95rem; }
th, td { text-align: left; padding: 10px 12px; border-bottom: 1px solid var(--border); }
th { background: var(--accent-soft); }
.table-scroll { overflow-x: auto; }

.formula {
  background: var(--surface); border-left: 4px solid var(--accent);
  padding: 12px 16px; border-radius: 0 8px 8px 0; font-family: ui-monospace, Consolas, monospace; font-size: 0.95rem;
  overflow-x: auto;
}
details { background: var(--surface); border: 1px solid var(--border); border-radius: 8px; padding: 12px 16px; margin: 10px 0; }
summary { font-weight: 600; cursor: pointer; }
.note { font-size: 0.9rem; color: var(--muted); }

.related { margin-top: 48px; }

/* Pie */
.site-footer { border-top: 1px solid var(--border); background: var(--surface); padding: 28px 0; font-size: 0.9rem; color: var(--muted); }
.site-footer .wrap { display: flex; justify-content: space-between; gap: 16px; flex-wrap: wrap; }
.site-footer a { color: var(--muted); margin-right: 16px; }
.site-footer .footer-calcs { display: block; margin-bottom: 20px; padding-bottom: 20px; border-bottom: 1px solid var(--border); }
.footer-calcs strong { display: block; color: var(--text); margin-bottom: 8px; }
.footer-calcs nav { display: flex; flex-wrap: wrap; gap: 6px 0; }