*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #0f1117;
  color: #e2e8f0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 2rem 1rem;
}

.site-header {
  text-align: center;
  margin-bottom: 1.5rem;
}

.site-header h1 {
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: #f1f5f9;
}

.site-header p {
  margin-top: 0.2rem;
  font-size: 0.75rem;
  color: #64748b;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

nav {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 2rem;
  background: #1e2330;
  border: 1px solid #2d3448;
  border-radius: 10px;
  padding: 0.35rem;
}

nav a {
  text-decoration: none;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: #64748b;
  padding: 0.45rem 1.1rem;
  border-radius: 7px;
  transition: background 0.15s, color 0.15s;
}

nav a:hover { color: #e2e8f0; }
nav a.active { background: #3b82f6; color: #fff; }

header {
  text-align: center;
  margin-bottom: 2rem;
}

header h1 {
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: #f1f5f9;
}

header p {
  margin-top: 0.35rem;
  font-size: 0.8rem;
  color: #64748b;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.card {
  background: #1e2330;
  border: 1px solid #2d3448;
  border-radius: 12px;
  padding: 1.75rem;
  width: 100%;
  max-width: 480px;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  margin-bottom: 1.25rem;
}

label {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: #94a3b8;
}

input[type="number"] {
  background: #0f1117;
  border: 1px solid #2d3448;
  border-radius: 8px;
  color: #f1f5f9;
  font-size: 1.1rem;
  padding: 0.6rem 0.8rem;
  width: 100%;
  outline: none;
  transition: border-color 0.15s;
}

input[type="number"]:focus { border-color: #3b82f6; }

.toggle-group {
  display: flex;
  gap: 0.5rem;
}

.toggle-group label {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  font-size: 0.8rem;
  cursor: pointer;
  background: #0f1117;
  border: 1px solid #2d3448;
  border-radius: 8px;
  padding: 0.55rem 0.75rem;
  text-transform: none;
  letter-spacing: normal;
  font-weight: 500;
  color: #94a3b8;
  transition: border-color 0.15s, color 0.15s;
}

.toggle-group input[type="radio"] { display: none; }
.toggle-group label:has(input:checked) { border-color: #3b82f6; color: #e2e8f0; }

button[type="submit"] {
  width: 100%;
  margin-top: 0.5rem;
  padding: 0.75rem;
  background: #3b82f6;
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  cursor: pointer;
  transition: background 0.15s;
}

button[type="submit"]:hover { background: #2563eb; }

#results { width: 100%; max-width: 480px; margin-top: 1.25rem; }

.result-card {
  background: #1e2330;
  border: 1px solid #2d3448;
  border-radius: 12px;
  padding: 1.5rem;
}

.result-card h2 {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: #64748b;
  margin-bottom: 1.1rem;
}

.result-row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding: 0.65rem 0;
  border-bottom: 1px solid #2d3448;
}

.result-row:last-of-type { border-bottom: none; }

.result-label { font-size: 0.85rem; color: #94a3b8; }

.result-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: #f1f5f9;
  font-variant-numeric: tabular-nums;
}

.result-value span {
  font-size: 0.8rem;
  font-weight: 400;
  color: #64748b;
  margin-left: 0.25rem;
}

.notes {
  margin-top: 1rem;
  padding: 0.75rem;
  background: #0f1117;
  border-radius: 8px;
  font-size: 0.75rem;
  color: #64748b;
  line-height: 1.6;
}

.notes strong { color: #94a3b8; }

/* Cruise two-column tank comparison */
.tank-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.5rem;
  margin-top: 0.75rem;
}

.tank-col {
  background: #0f1117;
  border-radius: 8px;
  padding: 0.75rem;
}

.tank-col h3 {
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: #3b82f6;
  margin-bottom: 0.6rem;
}

.tank-row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding: 0.3rem 0;
  border-bottom: 1px solid #1e2330;
}

.tank-row:last-child { border-bottom: none; }

.tank-label { font-size: 0.78rem; color: #64748b; }

.tank-value {
  font-size: 1rem;
  font-weight: 600;
  color: #f1f5f9;
  font-variant-numeric: tabular-nums;
}

.tank-value span {
  font-size: 0.72rem;
  font-weight: 400;
  color: #64748b;
  margin-left: 0.2rem;
}