/* ===== Reset & Base ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --bg: #0f1117;
  --surface: #1a1d27;
  --border: #2e3345;
  --text: #e8eaed;
  --muted: #9aa0b0;
  --accent: #6c63ff;
  --accent-hover: #5a52e0;
  --danger: #ff6b6b;
  --success: #51cf66;
  --warning: #ffd43b;
  --radius-card: 10px;
  --radius-input: 6px;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
}

/* ===== Layout ===== */
.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 16px;
}

header {
  text-align: center;
  padding: 40px 0 24px;
}

header h1 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 8px;
}

header p {
  color: var(--muted);
  font-size: 1.05rem;
  max-width: 560px;
  margin: 0 auto;
}

/* ===== Cards ===== */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-card);
  padding: 24px;
  margin-bottom: 20px;
}

.card h2 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 16px;
}

.card h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--muted);
}

/* ===== Form Controls ===== */
.form-row {
  display: flex;
  gap: 12px;
  margin-bottom: 14px;
  flex-wrap: wrap;
}

.form-group {
  flex: 1;
  min-width: 0;
}

.form-group label {
  display: block;
  font-size: 0.85rem;
  color: var(--muted);
  margin-bottom: 4px;
  font-weight: 500;
}

.form-group input,
.form-group select {
  width: 100%;
  padding: 10px 12px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  color: var(--text);
  font-size: 0.95rem;
  font-family: inherit;
  transition: border-color 0.2s;
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--accent);
}

.form-group input::placeholder {
  color: var(--muted);
  opacity: 0.6;
}

.form-group select option {
  background: var(--surface);
  color: var(--text);
}

/* ===== Toggle Switch ===== */
.toggle-group {
  display: inline-flex;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  overflow: hidden;
}

.toggle-group button {
  padding: 8px 16px;
  border: none;
  background: transparent;
  color: var(--muted);
  font-size: 0.85rem;
  font-family: inherit;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

.toggle-group button.active {
  background: var(--accent);
  color: #fff;
}

/* ===== Gender Toggle ===== */
.gender-toggle {
  display: flex;
  gap: 8px;
  margin-bottom: 14px;
}

.gender-toggle button {
  flex: 1;
  padding: 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  background: var(--bg);
  color: var(--muted);
  font-size: 0.95rem;
  font-family: inherit;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

.gender-toggle button.active {
  border-color: var(--accent);
  background: rgba(108, 99, 255, 0.1);
  color: var(--accent);
}

/* ===== Activity Level ===== */
.activity-options {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-bottom: 14px;
}

.activity-option {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  cursor: pointer;
  transition: all 0.2s;
}

.activity-option:hover {
  border-color: var(--accent);
}

.activity-option.active {
  border-color: var(--accent);
  background: rgba(108, 99, 255, 0.1);
}

.activity-option input[type="radio"] {
  display: none;
}

.activity-dot {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  border: 2px solid var(--border);
  flex-shrink: 0;
  transition: all 0.2s;
}

.activity-option.active .activity-dot {
  border-color: var(--accent);
  background: var(--accent);
  box-shadow: inset 0 0 0 3px var(--surface);
}

.activity-label {
  font-size: 0.9rem;
  font-weight: 500;
}

.activity-desc {
  font-size: 0.8rem;
  color: var(--muted);
  margin-left: auto;
}

/* ===== Formula Select ===== */
.formula-row {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 14px;
}

.formula-row label {
  font-size: 0.85rem;
  color: var(--muted);
  font-weight: 500;
  white-space: nowrap;
}

.formula-row select {
  flex: 1;
  padding: 10px 12px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  color: var(--text);
  font-size: 0.95rem;
  font-family: inherit;
}

.formula-row select:focus {
  outline: none;
  border-color: var(--accent);
}

/* ===== Body Fat ===== */
.body-fat-row {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 14px;
}

.body-fat-row label {
  font-size: 0.85rem;
  color: var(--muted);
  font-weight: 500;
  white-space: nowrap;
}

.body-fat-row input {
  width: 80px;
  padding: 10px 12px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  color: var(--text);
  font-size: 0.95rem;
  font-family: inherit;
}

.body-fat-row input:focus {
  outline: none;
  border-color: var(--accent);
}

.body-fat-row span {
  color: var(--muted);
  font-size: 0.85rem;
}

/* ===== Calculate Button ===== */
.btn-calculate {
  display: block;
  width: 100%;
  padding: 14px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: var(--radius-input);
  font-size: 1rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: background 0.2s;
}

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

/* ===== Results ===== */
#results {
  display: none;
}

#results.visible {
  display: block;
}

.result-hero {
  display: flex;
  gap: 16px;
  margin-bottom: 16px;
}

.result-box {
  flex: 1;
  text-align: center;
  padding: 20px 16px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
}

.result-box .label {
  font-size: 0.8rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 4px;
}

.result-box .value {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--accent);
}

.result-box .unit {
  font-size: 0.85rem;
  color: var(--muted);
  font-weight: 400;
}

.result-box.lean-mass .value {
  color: var(--success);
}

/* ===== Calorie Goals ===== */
.calorie-goals {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 10px;
}

.calorie-goal {
  padding: 14px 12px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  text-align: center;
}

.calorie-goal .goal-label {
  font-size: 0.75rem;
  color: var(--muted);
  margin-bottom: 4px;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.calorie-goal .goal-value {
  font-size: 1.25rem;
  font-weight: 700;
}

.calorie-goal .goal-delta {
  font-size: 0.75rem;
  margin-top: 2px;
}

.calorie-goal.loss .goal-value { color: var(--danger); }
.calorie-goal.loss .goal-delta { color: var(--danger); }
.calorie-goal.maintain .goal-value { color: var(--warning); }
.calorie-goal.maintain .goal-delta { color: var(--warning); }
.calorie-goal.gain .goal-value { color: var(--success); }
.calorie-goal.gain .goal-delta { color: var(--success); }

/* ===== Macro Calculator ===== */
.macro-controls {
  display: flex;
  gap: 12px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}

.macro-controls .form-group {
  min-width: 160px;
}

.macro-sliders {
  margin-bottom: 16px;
}

.macro-slider-row {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 10px;
}

.macro-slider-row label {
  width: 70px;
  font-size: 0.85rem;
  font-weight: 500;
  flex-shrink: 0;
}

.macro-slider-row input[type="range"] {
  flex: 1;
  -webkit-appearance: none;
  appearance: none;
  height: 6px;
  background: var(--border);
  border-radius: 3px;
  outline: none;
}

.macro-slider-row input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
}

.macro-slider-row input[type="range"]::-moz-range-thumb {
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent);
  border: none;
  cursor: pointer;
}

.macro-slider-row .pct {
  width: 42px;
  text-align: right;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--accent);
}

.macro-total-warning {
  font-size: 0.8rem;
  color: var(--danger);
  margin-bottom: 10px;
  display: none;
}

.macro-total-warning.visible {
  display: block;
}

.macro-results {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}

.macro-result {
  padding: 16px 12px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  text-align: center;
}

.macro-result .macro-name {
  font-size: 0.8rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.03em;
  margin-bottom: 4px;
}

.macro-result .macro-grams {
  font-size: 1.35rem;
  font-weight: 700;
}

.macro-result .macro-cals {
  font-size: 0.8rem;
  color: var(--muted);
  margin-top: 2px;
}

.macro-result.protein .macro-grams { color: #ff6b6b; }
.macro-result.carbs .macro-grams { color: #ffd43b; }
.macro-result.fat .macro-grams { color: #51cf66; }

.macro-calories-label {
  text-align: center;
  margin-top: 12px;
  font-size: 0.9rem;
  color: var(--muted);
}

.macro-calories-label strong {
  color: var(--accent);
}

/* ===== Collapsible ===== */
.collapsible-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  cursor: pointer;
  padding: 16px 0;
  user-select: none;
}

.collapsible-header h2 {
  margin-bottom: 0;
}

.collapsible-arrow {
  font-size: 1.1rem;
  color: var(--muted);
  transition: transform 0.2s;
}

.collapsible-header.open .collapsible-arrow {
  transform: rotate(180deg);
}

.collapsible-body {
  display: none;
  padding-bottom: 8px;
}

.collapsible-body.open {
  display: block;
}

.formula-block {
  margin-bottom: 16px;
}

.formula-block h3 {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 6px;
}

.formula-block p {
  font-size: 0.85rem;
  color: var(--muted);
  margin-bottom: 6px;
}

.formula-block code {
  display: block;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  padding: 10px 14px;
  font-size: 0.85rem;
  color: var(--accent);
  white-space: pre-wrap;
  line-height: 1.5;
  overflow-x: auto;
}

/* ===== Internal Links ===== */
.internal-links {
  margin: 32px 0 24px;
}

.internal-links h2 {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--muted);
}

.link-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 10px;
}

.link-grid a {
  display: block;
  padding: 14px 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  color: var(--text);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: border-color 0.2s;
}

.link-grid a:hover {
  border-color: var(--accent);
}

/* ===== Footer ===== */
footer {
  text-align: center;
  padding: 24px 0 32px;
  color: var(--muted);
  font-size: 0.8rem;
  border-top: 1px solid var(--border);
}

/* ===== Responsive ===== */
@media (max-width: 600px) {
  header h1 {
    font-size: 1.5rem;
  }

  .form-row {
    flex-direction: column;
    gap: 10px;
  }

  .result-hero {
    flex-direction: column;
  }

  .calorie-goals {
    grid-template-columns: repeat(2, 1fr);
  }

  .macro-results {
    grid-template-columns: 1fr;
  }

  .activity-desc {
    display: none;
  }

  .link-grid {
    grid-template-columns: 1fr 1fr;
  }
}