:root {
  --accent: #0f766e;
  --accent-dark: #0d5d56;
  --accent-light: #ccfbf1;
  --bg: #ffffff;
  --text: #1f2937;
  --text-muted: #6b7280;
  --border: #e5e7eb;
  --card-bg: #f9fafb;
  --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  font-size: 16px;
}

/* Nav */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: #ffffff;
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow);
}
.nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 12px 20px;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 18px;
}
.nav-brand {
  font-weight: 700;
  font-size: 18px;
  color: var(--accent);
  text-decoration: none;
  margin-right: auto;
}
.nav a.nav-link {
  color: var(--text);
  text-decoration: none;
  font-size: 14px;
  font-weight: 500;
  padding: 6px 10px;
  border-radius: 6px;
  transition: background 0.15s, color 0.15s;
}
.nav a.nav-link:hover { background: var(--accent-light); color: var(--accent-dark); }
.nav a.nav-link.active { color: var(--accent); background: var(--accent-light); }

/* Layout */
main {
  max-width: 900px;
  margin: 0 auto;
  padding: 24px 20px 60px;
}

h1 {
  font-size: 30px;
  margin: 16px 0 12px;
  color: var(--text);
  line-height: 1.25;
}
h2 {
  font-size: 22px;
  margin: 32px 0 12px;
  color: var(--text);
}
h3 {
  font-size: 18px;
  margin: 20px 0 10px;
  color: var(--accent-dark);
}
.intro {
  font-size: 16px;
  color: var(--text-muted);
  margin-bottom: 8px;
}

/* AdSense placeholder */
.adslot {
  min-height: 90px;
  background: #f3f4f6;
  text-align: center;
  padding: 10px;
  margin: 16px 0;
  border-radius: 6px;
  color: #999;
  font-size: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Calculator card */
.calc {
  background: #ffffff;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 24px;
  box-shadow: var(--shadow);
  margin: 16px 0;
}
.calc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
}
.field {
  display: flex;
  flex-direction: column;
}
.field label {
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text);
}
.field input,
.field select {
  padding: 10px 12px;
  font-size: 15px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: #ffffff;
  font-family: inherit;
  color: var(--text);
  transition: border-color 0.15s, box-shadow 0.15s;
}
.field input:focus,
.field select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(15, 118, 110, 0.15);
}

.btn {
  display: inline-block;
  background: var(--accent);
  color: #fff;
  border: none;
  padding: 11px 22px;
  font-size: 15px;
  font-weight: 600;
  border-radius: 6px;
  cursor: pointer;
  margin-top: 16px;
  font-family: inherit;
  transition: background 0.15s;
}
.btn:hover { background: var(--accent-dark); }

/* Results */
.results {
  background: var(--accent-light);
  border-left: 4px solid var(--accent);
  border-radius: 8px;
  padding: 20px;
  margin: 20px 0;
}
.results h3 {
  margin-top: 0;
  color: var(--accent-dark);
}
.result-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 8px 0;
  border-bottom: 1px solid rgba(15, 118, 110, 0.15);
  font-size: 15px;
}
.result-row:last-child { border-bottom: none; }
.result-row .label { color: var(--text); }
.result-row .value {
  font-weight: 700;
  color: var(--accent-dark);
  font-variant-numeric: tabular-nums;
}
.result-row.total {
  border-top: 2px solid var(--accent);
  margin-top: 6px;
  padding-top: 12px;
  font-size: 17px;
}
.result-row.total .value { color: var(--accent); font-size: 18px; }

/* Tables */
.table-wrap {
  overflow-x: auto;
  margin: 16px 0;
}
table {
  width: 100%;
  border-collapse: collapse;
  font-size: 15px;
}
th, td {
  padding: 10px 12px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}
th {
  background: var(--card-bg);
  font-weight: 600;
  color: var(--text);
}
td { font-variant-numeric: tabular-nums; }

/* Info box */
.info-box {
  background: #fffbeb;
  border-left: 4px solid #f59e0b;
  border-radius: 6px;
  padding: 14px 16px;
  margin: 20px 0;
  font-size: 14px;
  color: #78350f;
}
.info-box strong { color: #92400e; }

.note {
  font-size: 13px;
  color: var(--text-muted);
  font-style: italic;
  margin: 8px 0 0;
}

/* Footer */
footer {
  background: var(--card-bg);
  border-top: 1px solid var(--border);
  padding: 24px 20px;
  text-align: center;
  font-size: 13px;
  color: var(--text-muted);
  margin-top: 40px;
}
footer .footer-links {
  margin: 8px 0;
}
footer a {
  color: var(--accent);
  text-decoration: none;
  margin: 0 8px;
}
footer a:hover { text-decoration: underline; }
footer .disclaimer {
  display: block;
  margin-top: 6px;
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
}

/* Mobile */
@media (max-width: 640px) {
  h1 { font-size: 24px; }
  h2 { font-size: 19px; }
  .nav-inner { padding: 10px 14px; gap: 4px 10px; }
  .nav-brand { width: 100%; margin-bottom: 4px; }
  .nav a.nav-link { font-size: 13px; padding: 5px 8px; }
  main { padding: 16px 14px 40px; }
  .calc { padding: 16px; }
  .result-row { font-size: 14px; }
}