/* ============================================
   BASE – Variables, Reset, Typography
   ============================================ */

:root {
  --color-primary: #2563eb;
  --color-primary-hover: #3b82f6;
  --color-primary-muted: rgba(37, 99, 235, 0.15);
  --color-accent: #06b6d4;
  --color-accent-muted: rgba(6, 182, 212, 0.12);

  --color-success: #22c55e;
  --color-success-muted: rgba(34, 197, 94, 0.12);
  --color-warning: #eab308;
  --color-danger: #ef4444;
  --color-danger-muted: rgba(239, 68, 68, 0.12);

  --color-bg: #0b0f17;
  --color-bg-elevated: #111827;
  --color-bg-surface: #1a2332;
  --color-bg-hover: #243044;

  --color-border: rgba(148, 163, 184, 0.12);
  --color-border-strong: rgba(148, 163, 184, 0.22);

  --color-text: #f1f5f9;
  --color-text-muted: #94a3b8;
  --color-text-subtle: #64748b;

  --font-family: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
  --font-size-xs: 0.8125rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 2rem;
  --font-size-4xl: clamp(2rem, 4vw, 3rem);

  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  --spacing-3xl: 4rem;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;

  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.35);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.45);

  --transition: 0.2s ease;
  --header-height: 72px;
  --max-width: 1140px;
}

[data-theme="light"] {
  --color-bg: #f8fafc;
  --color-bg-elevated: #ffffff;
  --color-bg-surface: #f1f5f9;
  --color-bg-hover: #e2e8f0;
  --color-border: rgba(15, 23, 42, 0.08);
  --color-border-strong: rgba(15, 23, 42, 0.15);
  --color-text: #0f172a;
  --color-text-muted: #475569;
  --color-text-subtle: #64748b;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.1);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color var(--transition), color var(--transition);
  min-height: 100vh;
}

h1, h2, h3, h4 {
  line-height: 1.25;
  font-weight: 600;
  color: var(--color-text);
}

h1 { font-size: var(--font-size-4xl); }
h2 { font-size: var(--font-size-2xl); margin-bottom: var(--spacing-md); }
h3 { font-size: var(--font-size-xl); margin-bottom: var(--spacing-sm); }

p {
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-md);
}

p:last-child {
  margin-bottom: 0;
}

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

a:hover {
  color: var(--color-primary-hover);
}

.section-label {
  display: inline-block;
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-accent);
  margin-bottom: var(--spacing-sm);
}

.section-title {
  font-size: var(--font-size-2xl);
  margin-bottom: var(--spacing-sm);
}

.section-intro {
  max-width: 560px;
  margin-bottom: var(--spacing-xl);
}

.cache-hint {
  display: block;
  margin-top: var(--spacing-xs);
  font-size: var(--font-size-xs);
  color: var(--color-text-subtle);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}