:root {
  --bg: #f6f7fb;
  --bg-elev: #ffffff;
  --text: #1a1f2e;
  --muted: #5b6478;
  --border: #e3e6ee;
  --accent: #4f46e5;
  --accent-hover: #4338ca;
  --accent-soft: #eef0ff;
  --good: #10b981;
  --shadow: 0 1px 2px rgba(15, 23, 42, .04), 0 8px 24px rgba(15, 23, 42, .06);
  --radius: 12px;
  --radius-sm: 8px;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
}

[data-theme="dark"] {
  --bg: #0d1117;
  --bg-elev: #151b25;
  --text: #e6edf3;
  --muted: #8b95a8;
  --border: #232b38;
  --accent: #818cf8;
  --accent-hover: #a5b4fc;
  --accent-soft: #1e2433;
  --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 8px 24px rgba(0, 0, 0, .35);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  font-size: 15px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  background: var(--bg-elev);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 10;
  backdrop-filter: blur(8px);
}

.brand { display: flex; align-items: center; gap: 12px; }
.logo { font-size: 28px; }
.brand h1 { margin: 0; font-size: 18px; font-weight: 700; }
.tagline { margin: 0; color: var(--muted); font-size: 12px; }

.actions { display: flex; gap: 8px; }

button {
  font: inherit;
  cursor: pointer;
  border: 1px solid var(--border);
  background: var(--bg-elev);
  color: var(--text);
  padding: 8px 14px;
  border-radius: var(--radius-sm);
  transition: background .15s, border-color .15s, transform .05s;
}
button:hover { background: var(--accent-soft); border-color: var(--accent); }
button:active { transform: translateY(1px); }
button.ghost { background: transparent; }
button.full { width: 100%; }

.container {
  max-width: 1100px;
  margin: 24px auto;
  padding: 0 24px 40px;
}

.hint {
  color: var(--muted);
  margin: 0 0 20px;
  font-size: 14px;
}

.grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

@media (max-width: 760px) {
  .grid { grid-template-columns: 1fr; }
  .topbar { padding: 12px 16px; }
  .container { padding: 0 16px 32px; }
}

.card {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
}

.card h2 {
  margin: 0 0 16px;
  font-size: 15px;
  font-weight: 600;
  letter-spacing: .02em;
  text-transform: uppercase;
  color: var(--muted);
  border-bottom: 1px solid var(--border);
  padding-bottom: 10px;
}

.field { margin-bottom: 12px; }
.field label {
  display: block;
  font-size: 13px;
  color: var(--muted);
  margin-bottom: 4px;
}

input[type="number"], select {
  width: 100%;
  padding: 9px 11px;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text);
  border-radius: var(--radius-sm);
  font: inherit;
  font-variant-numeric: tabular-nums;
  outline: none;
  transition: border-color .15s, box-shadow .15s;
}

input[type="number"]:focus, select:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

/* Visually mark inputs that were auto-filled by the calculator */
input.auto-filled {
  background: var(--accent-soft);
  color: var(--accent-hover);
  font-weight: 500;
}
[data-theme="dark"] input.auto-filled { color: var(--accent); }

.row { display: flex; gap: 8px; }
.row input { flex: 1; }
.row select { flex: 0 0 80px; }

.three {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 10px;
}

.results { margin-top: 24px; }

.results-list {
  margin: 0;
  display: grid;
  grid-template-columns: 1fr auto;
  row-gap: 6px;
  column-gap: 16px;
  font-family: var(--mono);
  font-size: 13px;
}

.results-list dt {
  color: var(--muted);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}
.results-list dd {
  margin: 0;
  text-align: right;
  font-variant-numeric: tabular-nums;
}
.results-list dd.empty { color: var(--muted); opacity: .5; }
.results-list dd.fresh {
  animation: flash .6s ease-out;
}
@keyframes flash {
  0% { background: var(--accent-soft); }
  100% { background: transparent; }
}

.formulas {
  margin-top: 28px;
  padding: 16px 20px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 13px;
}
.formulas summary { cursor: pointer; color: var(--muted); font-weight: 500; }
.formulas ul { margin: 12px 0 0; padding-left: 20px; }
.formulas code {
  font-family: var(--mono);
  background: var(--bg);
  padding: 1px 6px;
  border-radius: 4px;
  border: 1px solid var(--border);
}

.foot {
  text-align: center;
  color: var(--muted);
  font-size: 12px;
  padding: 24px 16px 40px;
}

.seo-content {
  margin-top: 28px;
  padding: 24px 28px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 14px;
  line-height: 1.65;
  color: var(--text);
}
.seo-content h2 {
  margin: 0 0 12px;
  font-size: 18px;
}
.seo-content h3 {
  margin: 22px 0 8px;
  font-size: 15px;
}
.seo-content h4 {
  margin: 16px 0 4px;
  font-size: 14px;
  color: var(--accent);
}
.seo-content code {
  font-family: var(--mono);
  background: var(--bg);
  padding: 1px 6px;
  border-radius: 4px;
  border: 1px solid var(--border);
  font-size: 12.5px;
}
.seo-content ul { padding-left: 20px; }
.seo-content p { margin: 8px 0; }