:root {
  /* Theme transition */
  --theme-transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease, box-shadow 0.3s ease;

  /* Dynamic accent color (set via JS) */
  --color-accent: #ec4141;
  --color-accent-hover: color-mix(in srgb, var(--color-accent) 85%, white);
  --color-accent-soft: color-mix(in srgb, var(--color-accent) 10%, transparent);

  /* Typography */
  --font-family-base: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;

  /* Spacing & Radius */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --radius-xl: 24px;
  --radius-2xl: 32px;
  --radius-full: 9999px;

  --sidebar-width: 240px;
  --topbar-height: 64px;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-base: 0.25s ease;
  --transition-slow: 0.35s ease;
}

/* Dark Theme (default) */
:root,
[data-theme="dark"] {
  --color-bg-primary: #121212;
  --color-bg-secondary: #181818;
  --color-bg-tertiary: #282828;
  --color-bg-elevated: #2a2a2a;

  --color-text-primary: #ffffff;
  --color-text-secondary: #b3b3b3;
  --color-text-muted: #737373;

  --color-border: #2a2a2a;
  --color-border-light: #3a3a3a;

  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.12);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.16);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.24);
  --shadow-elevated: 0 12px 48px rgba(0, 0, 0, 0.32);
}

/* Light Theme */
[data-theme="light"] {
  --color-bg-primary: #ffffff;
  --color-bg-secondary: rgba(40, 50, 72, 0.03);
  --color-bg-tertiary: #ebebeb;
  --color-bg-elevated: #e0e0e0;

  --color-text-primary: #1a1a1a;
  --color-text-secondary: #5c5c5c;
  --color-text-muted: #8c8c8c;

  --color-border: #e0e0e0;
  --color-border-light: #d0d0d0;

  --shadow-sm: 0 2px 8px 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, 0.12);
  --shadow-elevated: 0 12px 48px rgba(0, 0, 0, 0.16);
}

/* Apply theme transition to common elements */
body,
.sidebar,
.topbar,
.settings-overlay,
.settings-container,
.settings-nav,
.settings-content,
.nav-item,
.setting-item,
.action-btn,
.toggle-slider {
  transition: var(--theme-transition);
}