:root {
  --bg: #ffffff;
  --text: #0f172a;
  --muted: #64748b;
  --accent: #2563eb;
  --border: #e2e8f0;

  /* Surface tokens — will be overridden by JS on color change */
  --surface: #ffffff;
  --surface-2: #f8fafc;
  --surface-3: #f1f5f9;
  --text-muted: #64748b;
  --code-bg: #0f172a;
  --code-text: #e2e8f0;

  --card-bg: var(--surface);
  --danger: #dc2626;
  --success: #16a34a;

  /* Design tokens */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-6: 24px;

  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;

  --fs-xs: 0.75rem;
  --fs-sm: 0.85rem;
  --fs-base: 1rem;
  --fs-lg: 1.25rem;
  --fs-xl: 1.75rem;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  transition: background-color 0.25s ease, color 0.25s ease;
}

.container {
  max-width: 720px;
  margin: 48px auto;
  padding: 0 16px;
}

h1 {
  font-size: 1.75rem;
  margin: 0 0 24px;
}

h2 {
  font-size: 1.25rem;
  margin: 0 0 12px;
}

h3 {
  font-size: 1rem;
  margin: 0 0 6px;
}

form {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 24px;
}

label {
  width: 100%;
  font-size: 0.9rem;
  color: var(--muted);
  margin-bottom: 4px;
}

input[type="text"] {
  flex: 1 1 200px;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 1rem;
  background: var(--surface);
  color: var(--text);
}

input[type="text"]::placeholder {
  color: var(--text-muted);
}

button {
  padding: 10px 16px;
  border: none;
  border-radius: 6px;
  background: var(--accent);
  color: #fff;
  font-size: 1rem;
  cursor: pointer;
}

button:hover {
  opacity: 0.9;
}

.preview {
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
  margin-bottom: 24px;
}

.preview-swatch {
  height: 160px;
  width: 100%;
  background: #f1f5f9;
  transition: background-color 0.25s ease;
}

.preview-info {
  padding: 12px 14px;
  font-size: 0.95rem;
  background: var(--surface-2);
  color: var(--text);
  border-top: 1px solid var(--border);
}

/* ---------- Cards for detail sections ---------- */
.card {
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px 18px;
  margin-bottom: 24px;
}

.card h2 {
  border-bottom: 1px solid var(--border);
  padding-bottom: 8px;
  margin-bottom: 14px;
}

.muted {
  color: var(--muted);
  font-size: 0.85rem;
  margin: 4px 0 0;
}

/* ---------- Color spaces grid ---------- */
.space-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 10px;
}

.space-card {
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 10px 12px;
  background: var(--surface-2);
  color: var(--text);
}

.space-card h3 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.muted {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin: 4px 0 0;
}

.space-values b {
  font-weight: 600;
  color: var(--text-muted);
}

.space-values {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 12px;
  font-size: 0.9rem;
}

.space-values b {
  font-weight: 600;
  color: var(--muted);
}

/* ---------- Base numbers table ---------- */
.base-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
}

.base-table th,
.base-table td {
  border: 1px solid var(--border);
  padding: 6px 8px;
  text-align: center;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  color: var(--text);
}

.base-table thead th {
  background: var(--surface-3);
}

.base-table th.red { color: var(--danger); }
.base-table th.green { color: var(--success); }
.base-table th.blue { color: var(--accent); }

/* ---------- Swatches ---------- */
.swatch-row {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 6px;
}

.swatch-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 8px;
}

.swatch-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  padding: 8px 6px;
  border-radius: 6px;
  text-decoration: none;
  color: inherit;
  border: 1px solid transparent;
  transition: background-color 0.15s ease, border-color 0.15s ease;
  text-align: center;
}

.swatch-item:hover {
  background: var(--surface-3);
  border-color: var(--border);
}

.swatch {
  display: block;
  width: 60px;
  height: 60px;
  border-radius: 6px;
  border: 1px solid rgba(128, 128, 128, 0.35);
  flex: 0 0 auto;
}

.swatch-label {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.75rem;
  line-height: 1.2;
  white-space: normal;
  word-break: break-word;
  color: var(--text);
}

/* ---------- Harmony blocks ---------- */
.harmony-block {
  padding: 10px 0;
  border-bottom: 1px dashed var(--border);
}

.harmony-block:last-child {
  border-bottom: none;
}

/* ---------- Code blocks ---------- */
pre {
  background: var(--code-bg);
  color: var(--code-text);
  padding: 12px 14px;
  border-radius: 6px;
  overflow-x: auto;
  font-size: 0.82rem;
  line-height: 1.45;
}

code {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
}

/* ---------- Responsive ---------- */
@media (max-width: 520px) {
  .container {
    margin: 24px auto;
  }

  .preview-swatch {
    height: 120px;
  }

  .space-grid {
    grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  }
}