/* IADU Design System — CSS Custom Properties
   Single source of truth. Never hardcode values in other files. */

:root {

  /* ─── Colors: Dark ─────────────────────────────────────── */
  --color-dark:        #0E0E12;
  --color-dark-2:      #16161C;
  --color-dark-3:      #1E1E26;
  --color-dark-border: #2A2A35;

  /* ─── Colors: Light ────────────────────────────────────── */
  --color-white:        #FFFFFF;
  --color-off-white:    #F7F8FA;
  --color-light-gray:   #F0F1F5;
  --color-border:       #E5E7EB;
  --color-light:        var(--color-off-white);
  --color-light-border: var(--color-border);

  /* ─── Colors: Accent (steel blue) ─────────────────────── */
  --color-accent:       #1D6FA4;
  --color-accent-hover: #155983;
  --color-accent-light: #EBF4FB;
  --color-accent-dark:  #0F4C75;

  /* ─── Colors: Text ─────────────────────────────────────── */
  --color-text:           #0E0E12;
  --color-text-primary:   var(--color-text);
  --color-text-secondary: #6B7280;
  --color-text-light:     #9CA3AF;
  --color-text-on-dark:   #F7F8FA;
  --color-text-on-dark-2: #9CA3AF;

  /* ─── Colors: Semantic tags ────────────────────────────── */
  --color-tag-paper:   #1D6FA4;
  --color-tag-report:  #0F766E;
  --color-tag-book:    #7C3AED;
  --color-tag-course:  #B45309;

  /* ─── Typography ────────────────────────────────────────── */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;

  --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;
  --text-6xl:  3.75rem;

  --leading-tight:   1.2;
  --leading-snug:    1.35;
  --leading-normal:  1.6;
  --leading-relaxed: 1.75;

  --tracking-tight:  -0.02em;
  --tracking-normal: 0;
  --tracking-wide:   0.05em;
  --tracking-wider:  0.1em;

  /* ─── Spacing ───────────────────────────────────────────── */
  --space-1:  0.25rem;
  --space-2:  0.5rem;
  --space-3:  0.75rem;
  --space-4:  1rem;
  --space-5:  1.25rem;
  --space-6:  1.5rem;
  --space-8:  2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;
  --space-32: 8rem;

  --section-y:    var(--space-20);
  --section-x:    var(--space-6);
  --container:    1200px;
  --container-wide: 1440px;

  /* ─── Border radius ─────────────────────────────────────── */
  --radius-sm: 3px;
  --radius:    6px;
  --radius-lg: 10px;
  --radius-xl: 16px;

  /* ─── Shadows ───────────────────────────────────────────── */
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow:    0 4px 12px rgba(0,0,0,0.08), 0 2px 4px rgba(0,0,0,0.04);
  --shadow-md: 0 6px 18px rgba(0,0,0,0.09), 0 3px 6px rgba(0,0,0,0.05);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.10), 0 4px 8px rgba(0,0,0,0.06);
  --shadow-xl: 0 16px 40px rgba(0,0,0,0.12);

  /* ─── Transitions ───────────────────────────────────────── */
  --transition:      150ms ease;
  --transition-med:  250ms ease;
  --transition-slow: 400ms ease;

  /* ─── Navigation ────────────────────────────────────────── */
  --nav-height:  76px;
  --nav-bg:      var(--color-dark);
  --nav-text:    var(--color-text-on-dark);
  --nav-border:  var(--color-dark-border);
  --nav-z:       1000;

  /* ─── Grid ──────────────────────────────────────────────── */
  --grid-gap:    var(--space-6);
  --grid-gap-lg: var(--space-8);
}