/* ============================================================
   Design System — base.css
   Study guide for AI interview transcript
   ============================================================ */

:root {
  --color-primary:   #7c3aed;
  --color-secondary: #0d9488;
  --color-accent:    #f59e0b;
  --color-success:   #10b981;
  --color-rose:      #f43f5e;
  --color-indigo:    #6366f1;
  --color-purple:    #8b5cf6;

  --gray-50:  #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;

  --space-xs:   4px;
  --space-sm:   8px;
  --space-md:   12px;
  --space-lg:   16px;
  --space-xl:   24px;
  --space-2xl:  32px;
  --space-3xl:  48px;

  --radius-sm:  4px;
  --radius-md:  8px;
  --radius-lg:  12px;
  --radius-xl:  16px;

  --shadow-sm:  0 1px  2px rgba(0, 0, 0, 0.05);
  --shadow-md:  0 4px  6px rgba(0, 0, 0, 0.07),
                0 2px  4px rgba(0, 0, 0, 0.05);
  --shadow-lg:  0 10px 15px rgba(0, 0, 0, 0.08),
                0 4px   6px rgba(0, 0, 0, 0.04);
  --shadow-xl:  0 20px 25px rgba(0, 0, 0, 0.10),
                0 8px  10px rgba(0, 0, 0, 0.04);

  --transition-fast:   0.15s ease;
  --transition-normal: 0.25s ease;
  --transition-slow:   0.35s ease;

  --font-heading: Georgia, 'PT Serif', serif;
  --font-body:    system-ui, -apple-system, 'Segoe UI', Roboto,
                  Helvetica, Arial, sans-serif;
  --font-code:    'SF Mono', SFMono-Regular, ui-monospace,
                  'Cascadia Code', 'Fira Code', Menlo, 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:  2rem;
  --text-4xl:  2.5rem;
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--gray-900);
  background-color: var(--gray-50);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img, picture, video, canvas, svg {
  display: block;
  max-width: 100%;
}

input, button, textarea, select {
  font: inherit;
}

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

a:hover {
  color: var(--color-indigo);
  text-decoration: underline;
}

h1, h2, h3, h4 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.25;
  color: var(--gray-900);
}

h1 { font-size: var(--text-4xl); letter-spacing: -0.025em; margin-bottom: var(--space-xl); }
h2 { font-size: var(--text-3xl); letter-spacing: -0.02em; margin-bottom: var(--space-lg); }
h3 { font-size: var(--text-2xl); margin-bottom: var(--space-md); }
h4 { font-size: var(--text-lg); margin-bottom: var(--space-sm); }

p { margin-bottom: var(--space-lg); }

@keyframes fadeIn {
  from { opacity: 0; }
  to   { opacity: 1; }
}

@keyframes slideIn {
  from { opacity: 0; transform: translateY(20px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50%      { transform: scale(1.05); }
}

.container {
  width: 100%;
  max-width: 1200px;
  margin-inline: auto;
  padding-inline: var(--space-lg);
}

@media (min-width: 768px) {
  .container { padding-inline: var(--space-xl); }
}

@media (min-width: 1024px) {
  h1 { font-size: calc(var(--text-4xl) * 1.15); }
  h2 { font-size: calc(var(--text-3xl) * 1.1); }
  .container { padding-inline: var(--space-2xl); }
}