/* AquaCalc — clean, fast, mobile-first styles */
:root {
  --bg: #f7fafc;
  --card: #ffffff;
  --ink: #1a2b3c;
  --muted: #5b6b7c;
  --brand: #0e7c86;
  --brand-dark: #0a5f66;
  --accent: #f2a541;
  --line: #e3ebf0;
  --radius: 12px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.65;
}
a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Header */
.site-header {
  background: var(--card);
  border-bottom: 1px solid var(--line);
  position: sticky; top: 0; z-index: 50;
}
.header-inner {
  max-width: 1080px; margin: 0 auto; padding: 12px 20px;
  display: flex; align-items: center; gap: 18px;
}
.logo { font-size: 1.35rem; font-weight: 800; color: var(--brand-dark); white-space: nowrap; }
.logo:hover { text-decoration: none; }
.logo span { color: var(--accent); }
.main-nav { display: flex; gap: 14px; margin-left: auto; flex-wrap: wrap; }
.main-nav a { color: var(--ink); font-size: .95rem; }
.lang-toggle {
  border: 1px solid var(--brand); background: #fff; color: var(--brand-dark);
  border-radius: 999px; padding: 6px 14px; font-size: .85rem; cursor: pointer; white-space: nowrap;
}
.lang-toggle:hover { background: var(--brand); color: #fff; text-decoration: none; }

/* Layout */
.wrap { max-width: 1080px; margin: 0 auto; padding: 24px 20px 60px; }
.hero { text-align: center; padding: 36px 0 10px; }
.hero h1 { font-size: 2rem; margin: 0 0 10px; }
.hero p { color: var(--muted); max-width: 640px; margin: 0 auto; }

/* Tool grid */
.tool-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 18px; margin: 28px 0;
}
.tool-card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 20px; display: block; color: var(--ink);
  transition: transform .12s ease, box-shadow .12s ease;
}
.tool-card:hover { text-decoration: none; transform: translateY(-2px); box-shadow: 0 8px 24px rgba(14,124,134,.12); }
.tool-card h3 { margin: 0 0 8px; font-size: 1.1rem; color: var(--brand-dark); }
.tool-card p { margin: 0; color: var(--muted); font-size: .92rem; }
.tool-icon { font-size: 1.8rem; }

/* Calculator */
.calculator {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 26px; margin: 26px 0; box-shadow: 0 2px 10px rgba(0,0,0,.03);
}
.calculator h2 { margin-top: 0; font-size: 1.25rem; }
.field { margin-bottom: 16px; }
.field label { display: block; font-weight: 600; margin-bottom: 6px; font-size: .95rem; }
.field input, .field select {
  width: 100%; padding: 10px 12px; font-size: 1rem;
  border: 1px solid var(--line); border-radius: 8px; background: #fff; color: var(--ink);
}
.field-row { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
@media (max-width: 560px) { .field-row { grid-template-columns: 1fr; } }
.btn {
  background: var(--brand); color: #fff; border: 0; border-radius: 8px;
  padding: 12px 26px; font-size: 1rem; font-weight: 700; cursor: pointer;
}
.btn:hover { background: var(--brand-dark); }
.result {
  display: none; margin-top: 20px; padding: 18px 20px;
  background: #eef7f8; border-left: 4px solid var(--brand); border-radius: 0 8px 8px 0;
}
.result.show { display: block; }
.result .big { font-size: 1.6rem; font-weight: 800; color: var(--brand-dark); }
.result p { margin: 6px 0; }
.hint { font-size: .85rem; color: var(--muted); }

/* Article */
.article { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 26px; margin: 26px 0; }
.article h2 { font-size: 1.3rem; margin-top: 28px; color: var(--brand-dark); }
.article h2:first-child { margin-top: 0; }
.article table { width: 100%; border-collapse: collapse; margin: 14px 0; font-size: .93rem; }
.article th, .article td { border: 1px solid var(--line); padding: 9px 12px; text-align: left; }
.article th { background: #eef4f6; }
.faq h3 { font-size: 1.02rem; margin: 18px 0 6px; }
.faq p { margin: 0 0 10px; color: #33475c; }

/* Ad placeholders */
.ad-slot {
  margin: 26px 0; padding: 14px; text-align: center;
  border: 1px dashed #b9c9d2; border-radius: 8px; background: #fbfdff;
  color: #93a5b1; font-size: .8rem;
}

/* Breadcrumbs */
.crumbs { font-size: .85rem; color: var(--muted); margin-bottom: 8px; }

/* Related */
.related { margin-top: 30px; }
.related ul { columns: 2; padding-left: 20px; }
@media (max-width: 560px) { .related ul { columns: 1; } }

/* Footer */
.site-footer { background: #12242f; color: #b9c9d4; margin-top: 40px; }
.footer-inner { max-width: 1080px; margin: 0 auto; padding: 36px 20px; display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 24px; }
.site-footer h4 { color: #fff; margin: 0 0 10px; font-size: 1rem; }
.site-footer a { color: #b9c9d4; font-size: .9rem; display: block; margin-bottom: 6px; }
.site-footer p { font-size: .85rem; }
.copy { text-align: center; padding: 16px; font-size: .8rem; color: #7d929f; border-top: 1px solid #1e3442; }

/* Diagram */
.diagram { text-align: center; margin: 18px 0; }
.diagram svg { max-width: 100%; height: auto; }