:root {
  --color-bg-primary: #0a0e1a;
  --color-bg-secondary: #111827;
  --color-bg-tertiary: #1a2332;
  --color-bg-elevated: #1f2b3d;

  --color-text-primary: #f0f4f8;
  --color-text-secondary: #94a3b8;
  --color-text-tertiary: #64748b;

  --color-accent: #3b82f6;
  --color-accent-hover: #2563eb;
  --color-purple: #8b5cf6;
  --color-cyan: #06b6d4;
  --color-green: #10b981;
  --color-red: #ef4444;
  --color-amber: #f59e0b;

  --gradient-hero: linear-gradient(135deg, #0a0e1a 0%, #1a1a4e 40%, #0f172a 70%, #0a0e1a 100%);
  --gradient-accent: linear-gradient(135deg, #3b82f6, #8b5cf6);
  --gradient-card: linear-gradient(135deg, rgba(59,130,246,0.08), rgba(139,92,246,0.08));
  --gradient-border: linear-gradient(135deg, rgba(59,130,246,0.4), rgba(139,92,246,0.4));

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", "Source Code Pro", Consolas, monospace;

  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 1.875rem;
  --text-4xl: 2.25rem;
  --text-5xl: 3rem;

  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  --max-width: 1200px;
  --header-height: 64px;
  --radius: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.5);
  --shadow-glow: 0 0 30px rgba(59,130,246,0.15);

  --transition: 250ms ease;
  --transition-fast: 150ms ease;
}

/* ============ Light theme overrides ============ */
[data-theme="light"] {
  --color-bg-primary: #f8fafc;
  --color-bg-secondary: #ffffff;
  --color-bg-tertiary: #f1f5f9;
  --color-bg-elevated: #e2e8f0;

  --color-text-primary: #0f172a;
  --color-text-secondary: #475569;
  --color-text-tertiary: #94a3b8;

  --gradient-hero: linear-gradient(135deg, #f8fafc 0%, #e0e7ff 40%, #f0f4ff 70%, #f8fafc 100%);
  --gradient-card: linear-gradient(135deg, rgba(59,130,246,0.05), rgba(139,92,246,0.05));
  --gradient-border: linear-gradient(135deg, rgba(59,130,246,0.25), rgba(139,92,246,0.25));

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.10);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);
  --shadow-glow: 0 0 30px rgba(59,130,246,0.20);
}
[data-theme="light"] body { background: var(--color-bg-primary); color: var(--color-text-primary); }
[data-theme="light"] .header { background: rgba(255,255,255,0.85); border-bottom: 1px solid rgba(0,0,0,0.06); }
[data-theme="light"] .header.scrolled { background: rgba(255,255,255,0.95); }
[data-theme="light"] .card,
[data-theme="light"] .auth-box,
[data-theme="light"] .pricing-card,
[data-theme="light"] .feature-card,
[data-theme="light"] .stat-card { border-color: rgba(0,0,0,0.08); background: var(--color-bg-secondary); }
[data-theme="light"] .footer { background: var(--color-bg-tertiary); border-top: 1px solid rgba(0,0,0,0.06); }
[data-theme="light"] .form-input { background: var(--color-bg-primary); border-color: rgba(0,0,0,0.12); color: var(--color-text-primary); }
[data-theme="light"] pre,
[data-theme="light"] .key-value,
[data-theme="light"] code { background: var(--color-bg-tertiary); color: var(--color-text-primary); }

/* Theme toggle button */
.theme-toggle { background: transparent; border: 1px solid rgba(255,255,255,0.12); color: var(--color-text-secondary); padding: 4px 8px; border-radius: var(--radius); cursor: pointer; margin-right: var(--space-2); display: inline-flex; align-items: center; font-size: 14px; line-height: 1; transition: all 0.2s; }
.theme-toggle:hover { color: var(--color-text-primary); border-color: var(--color-accent); }
[data-theme="light"] .theme-toggle { border-color: rgba(0,0,0,0.12); }