/* ═══════════════════════════════════════════════════════════════
   TF Study Shelf — Design Tokens
   All CSS custom properties from PRD 05 UI/UX Requirements
   ═══════════════════════════════════════════════════════════════ */

/* ─── Fonts ───────────────────────────────────────────────── */
@import url('https://fonts.googleapis.com/css2?family=Manrope:wght@400;500;600;700&display=swap');

@font-face {
  font-family: 'Geist Mono';
  src: url('https://cdn.jsdelivr.net/npm/geist@1.2.0/dist/fonts/geist-mono/GeistMono-Regular.woff2') format('woff2');
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'Geist Mono';
  src: url('https://cdn.jsdelivr.net/npm/geist@1.2.0/dist/fonts/geist-mono/GeistMono-Medium.woff2') format('woff2');
  font-weight: 500;
  font-style: normal;
  font-display: swap;
}

/* ─── Light Mode (default) ────────────────────────────────── */
:root {
  /* Base Colors */
  --color-primary-dark: #212121;
  --color-accent: #FF7759;
  --color-off-white: #FAFAFA;

  /* Theme-Aware Semantic Tokens */
  --bg-primary: #FAFAFA;
  --bg-surface: #FFFFFF;
  --bg-elevated: rgba(33, 33, 33, 0.04);
  --text-primary: #212121;
  --text-secondary: rgba(33, 33, 33, 0.6);
  --text-tertiary: rgba(33, 33, 33, 0.38);
  --border: rgba(33, 33, 33, 0.12);
  --accent: #FF7759;
  --accent-on: #FAFAFA;

  /* Alpha Variants */
  --color-border-light: rgba(33, 33, 33, 0.12);
  --color-surface-elevated: rgba(33, 33, 33, 0.04);
  --color-accent-hover: rgba(255, 119, 89, 0.85);
  --color-accent-pressed: rgba(255, 119, 89, 0.7);
  --color-accent-subtle: rgba(255, 119, 89, 0.1);
  --color-disabled: rgba(33, 33, 33, 0.38);
  --color-overlay: rgba(33, 33, 33, 0.5);
  --color-input-bg: rgba(33, 33, 33, 0.04);
  --color-input-placeholder: rgba(33, 33, 33, 0.4);
  --color-input-border: rgba(33, 33, 33, 0.2);

  /* Gradient */
  --gradient-primary: linear-gradient(135deg, #FF7759 0%, #212121 100%);
  --gradient-accent-soft: linear-gradient(135deg, rgba(255,119,89,0.15) 0%, rgba(33,33,33,0.05) 100%);

  /* Typography */
  --font-primary: 'Manrope', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'Geist Mono', 'SF Mono', 'Fira Code', monospace;

  /* Spacing */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;

  /* Border Radius */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 999px;

  /* Shadows */
  --shadow-1: 0 1px 3px rgba(0, 0, 0, 0.08);
  --shadow-2: 0 2px 8px rgba(0, 0, 0, 0.12);
  --shadow-3: 0 4px 16px rgba(0, 0, 0, 0.16);
  --shadow-4: 0 8px 32px rgba(0, 0, 0, 0.20);

  /* Transitions */
  --transition-fast: 150ms ease-out;
  --transition-normal: 300ms ease-in-out;
  --transition-slow: 500ms ease-out;
  --transition-sheet: 350ms cubic-bezier(0.4, 0, 0.2, 1);

  /* Layout */
  --sidebar-width: 260px;
  --topbar-height: 64px;
  --content-max-width: 1200px;
}

/* ─── Dark Mode ───────────────────────────────────────────── */
[data-theme="dark"] {
  --bg-primary: #212121;
  --bg-surface: #2A2A2A;
  --bg-elevated: rgba(250, 250, 250, 0.06);
  --text-primary: #FAFAFA;
  --text-secondary: rgba(250, 250, 250, 0.6);
  --text-tertiary: rgba(250, 250, 250, 0.38);
  --border: rgba(250, 250, 250, 0.12);
  --accent: #FF7759;
  --accent-on: #FAFAFA;
  --color-border-light: rgba(250, 250, 250, 0.12);
  --color-surface-elevated: rgba(250, 250, 250, 0.06);
  --color-input-bg: rgba(250, 250, 250, 0.08);
  --color-input-placeholder: rgba(250, 250, 250, 0.4);
  --color-input-border: rgba(250, 250, 250, 0.2);
  --color-overlay: rgba(0, 0, 0, 0.6);
  --color-disabled: rgba(250, 250, 250, 0.38);
  --shadow-1: 0 1px 3px rgba(0, 0, 0, 0.24);
  --shadow-2: 0 2px 8px rgba(0, 0, 0, 0.32);
  --shadow-3: 0 4px 16px rgba(0, 0, 0, 0.40);
  --shadow-4: 0 8px 32px rgba(0, 0, 0, 0.48);
}

/* ─── Typography Scale ────────────────────────────────────── */
.text-display-large   { font: 700 32px/40px var(--font-primary); }
.text-display-medium  { font: 700 28px/36px var(--font-primary); }
.text-headline        { font: 600 24px/32px var(--font-primary); }
.text-title-large     { font: 600 20px/28px var(--font-primary); }
.text-title-medium    { font: 600 16px/24px var(--font-primary); }
.text-body-large      { font: 400 16px/24px var(--font-primary); }
.text-body-medium     { font: 400 14px/20px var(--font-primary); }
.text-body-small      { font: 400 12px/16px var(--font-primary); }
.text-label-large     { font: 500 14px/20px var(--font-primary); }
.text-label-medium    { font: 500 12px/16px var(--font-primary); }
.text-label-small     { font: 500 10px/14px var(--font-primary); }
.text-mono            { font-family: var(--font-mono); }