:root {
  --bg: #fffbf3;
  --surface: #ffffff;
  --card: #fff8e7;
  --accent: #f59e0b;
  --accent-hover: #d97706;
  --accent-text: #ffffff;
  --text: #1c1917;
  --text-muted: #78716c;
  --border: #e7e5e4;
  --input-bg: #ffffff;
  --shadow: 0 1px 3px rgba(0,0,0,0.08);
  --radius: 8px;
  --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

[data-theme="beach"] {
  --bg: #f0f9ff;
  --surface: #ffffff;
  --card: #e0f2fe;
  --accent: #0891b2;
  --accent-hover: #0e7490;
  --accent-text: #ffffff;
  --text: #0c4a6e;
  --text-muted: #6b7280;
  --border: #bae6fd;
  --input-bg: #ffffff;
  --shadow: 0 1px 3px rgba(8,145,178,0.1);
}

[data-theme="rainstorm"] {
  --bg: #1f2937;
  --surface: #374151;
  --card: #4b5563;
  --accent: #818cf8;
  --accent-hover: #6366f1;
  --accent-text: #ffffff;
  --text: #f9fafb;
  --text-muted: #9ca3af;
  --border: #6b7280;
  --input-bg: #374151;
  --shadow: 0 1px 3px rgba(0,0,0,0.3);
}

[data-theme="chalet"] {
  --bg: #fdf6e3;
  --surface: #fffbf3;
  --card: #f4e9c9;
  --accent: #92400e;
  --accent-hover: #78350f;
  --accent-text: #ffffff;
  --text: #3c2005;
  --text-muted: #7c5c3a;
  --border: #d6b896;
  --input-bg: #fffbf3;
  --shadow: 0 1px 3px rgba(60,32,5,0.1);
}

[data-theme="midnight"] {
  --bg: #0f172a;
  --surface: #1e293b;
  --card: #1e293b;
  --accent: #38bdf8;
  --accent-hover: #0ea5e9;
  --accent-text: #0f172a;
  --text: #f1f5f9;
  --text-muted: #94a3b8;
  --border: #334155;
  --input-bg: #0f172a;
  --shadow: 0 1px 3px rgba(0,0,0,0.4);
}

[data-theme="wow"] {
  --bg: #000000;
  --surface: #111111;
  --card: #0a0a0a;
  --accent: #39ff14;
  --accent-hover: #00e600;
  --accent-text: #000000;
  --text: #ffffff;
  --text-muted: #cccccc;
  --border: #39ff14;
  --input-bg: #111111;
  --shadow: 0 0 10px rgba(57,255,20,0.2);
}

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

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  min-height: 100vh;
  transition: background 0.2s, color 0.2s;
}

/* Nav */
.nav {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  gap: 1.5rem;
  height: 56px;
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-logo {
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--accent);
  text-decoration: none;
  white-space: nowrap;
}

.nav-links {
  display: flex;
  gap: 1rem;
  flex: 1;
  overflow-x: auto;
  scrollbar-width: none;
}

.nav-links::-webkit-scrollbar { display: none; }

.nav-links a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.9rem;
  white-space: nowrap;
  padding: 0.25rem 0;
  border-bottom: 2px solid transparent;
  transition: color 0.15s, border-color 0.15s;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.theme-picker {
  display: flex;
  gap: 4px;
  margin-left: auto;
  flex-shrink: 0;
}

.theme-btn {
  width: 26px;
  height: 26px;
  border-radius: 50%;
  border: 2px solid transparent;
  cursor: pointer;
  font-size: 15px;
  line-height: 1;
  background: none;
  transition: transform 0.15s, border-color 0.15s;
  padding: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

.theme-btn:hover { transform: scale(1.25); }
.theme-btn.active { border-color: var(--accent); }

/* Main */
.main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

/* Hero */
.hero {
  text-align: center;
  padding: 3rem 0 1.5rem;
}

.hero h1 {
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 800;
  margin-bottom: 0.5rem;
}

.hero p {
  color: var(--text-muted);
  font-size: 1.05rem;
}

/* Calculator grid */
.calc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 1rem;
  margin-top: 2.5rem;
}

.calc-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow);
  transition: transform 0.15s, box-shadow 0.15s, border-color 0.15s;
  display: block;
}

.calc-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.12);
  border-color: var(--accent);
}

.calc-card-icon {
  font-size: 2rem;
  margin-bottom: 0.75rem;
}

.calc-card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.calc-card p {
  font-size: 0.85rem;
  color: var(--text-muted);
  line-height: 1.4;
}

.calc-card .cta {
  display: inline-block;
  margin-top: 0.75rem;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent);
}

/* Calculator page */
.calc-page {
  max-width: 680px;
}

.calc-header {
  margin-bottom: 2rem;
}

.calc-header h1 {
  font-size: 1.8rem;
  font-weight: 700;
}

.calc-header p {
  color: var(--text-muted);
  margin-top: 0.25rem;
}

.calc-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.75rem;
  box-shadow: var(--shadow);
}

.field {
  margin-bottom: 1.25rem;
}

.field label {
  display: block;
  font-size: 0.85rem;
  font-weight: 500;
  margin-bottom: 0.4rem;
  color: var(--text-muted);
}

.field input,
.field select {
  width: 100%;
  padding: 0.6rem 0.85rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--input-bg);
  color: var(--text);
  font-size: 1rem;
  font-family: inherit;
  transition: border-color 0.15s;
  outline: none;
  -webkit-appearance: none;
  appearance: none;
}

.field select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%23999' stroke-width='1.5' fill='none' stroke-linecap='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.85rem center;
  padding-right: 2.5rem;
}

.field input:focus,
.field select:focus {
  border-color: var(--accent);
}

.field-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

.calc-btn {
  width: 100%;
  padding: 0.75rem;
  background: var(--accent);
  color: var(--accent-text);
  border: none;
  border-radius: 6px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  font-family: inherit;
  transition: background 0.15s;
  margin-top: 0.25rem;
}

.calc-btn:hover { background: var(--accent-hover); }

/* Results */
.results {
  margin-top: 1.5rem;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  display: none;
}

.results.show { display: block; }

.results h3 {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

.result-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--border);
}

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

.result-label {
  font-size: 0.9rem;
  color: var(--text-muted);
}

.result-value {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text);
}

.result-value.accent { color: var(--accent); }

/* Tabs */
.tabs {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.25rem;
  flex-wrap: wrap;
}

.tab {
  padding: 0.4rem 1rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: none;
  color: var(--text-muted);
  font-size: 0.85rem;
  cursor: pointer;
  transition: all 0.15s;
  font-family: inherit;
}

.tab.active {
  background: var(--accent);
  color: var(--accent-text);
  border-color: var(--accent);
}

/* Toggle (metric/imperial) */
.toggle-row {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 1.25rem;
  font-size: 0.9rem;
}

.toggle {
  position: relative;
  width: 44px;
  height: 24px;
  flex-shrink: 0;
}

.toggle input { opacity: 0; width: 0; height: 0; position: absolute; }

.toggle-slider {
  position: absolute;
  inset: 0;
  background: var(--border);
  border-radius: 24px;
  cursor: pointer;
  transition: background 0.15s;
}

.toggle-slider:before {
  content: '';
  position: absolute;
  width: 18px;
  height: 18px;
  left: 3px;
  top: 3px;
  background: white;
  border-radius: 50%;
  transition: transform 0.15s;
}

.toggle input:checked + .toggle-slider { background: var(--accent); }
.toggle input:checked + .toggle-slider:before { transform: translateX(20px); }

/* BMI meter */
.bmi-meter {
  margin: 1.25rem 0 0.5rem;
  height: 8px;
  border-radius: 4px;
  background: linear-gradient(to right, #3b82f6 0%, #22c55e 35%, #f59e0b 65%, #ef4444 100%);
  position: relative;
}

.bmi-labels {
  display: flex;
  justify-content: space-between;
  font-size: 0.7rem;
  color: var(--text-muted);
  margin-top: 0.3rem;
  margin-bottom: 1rem;
}

.bmi-indicator {
  position: absolute;
  top: -5px;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--text);
  border: 2px solid var(--surface);
  transform: translateX(-50%);
  transition: left 0.3s ease;
}

/* Footer */
.footer {
  text-align: center;
  padding: 2rem;
  color: var(--text-muted);
  font-size: 0.8rem;
  margin-top: 4rem;
  border-top: 1px solid var(--border);
}

@media (max-width: 600px) {
  .field-row { grid-template-columns: 1fr; }
  .nav-links { display: none; }
  .hero { padding: 2rem 0 1rem; }
}