/* ==========================================================================
   Main CSS - Design Tokens, Typography, and Base Styles
   ========================================================================== */

/* Design Tokens (CSS Custom Properties) */
:root {
  /* Colors */
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-primary-light: #3b82f6;
  --color-secondary: #64748b;
  --color-accent: #0891b2;

  --color-text-primary: #1f2937;
  --color-text-secondary: #4b5563;
  --color-text-muted: #6b7280;
  --color-text-inverse: #ffffff;

  --color-background: #ffffff;
  --color-surface: #f8fafc;
  --color-surface-elevated: #ffffff;
  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;

  --color-success: #16a34a;
  --color-error: #dc2626;
  --color-warning: #d97706;

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;

  --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;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;
  --font-size-5xl: 3rem;

  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;

  --line-height-tight: 1.25;
  --line-height-normal: 1.5;
  --line-height-relaxed: 1.625;
  --line-height-loose: 2;

  --letter-spacing-tight: -0.025em;
  --letter-spacing-normal: 0;
  --letter-spacing-wide: 0.025em;

  /* 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;

  /* Layout */
  --container-max: 1200px;
  --container-narrow: 800px;
  --container-padding: var(--space-6);
  --section-padding: var(--space-20);
  --section-padding-mobile: var(--space-12);

  /* Effects */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);

  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  --transition-fast: 150ms ease;
  --transition-normal: 300ms ease;
  --transition-slow: 500ms ease;

  /* Z-index scale */
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-fixed: 300;
  --z-modal-backdrop: 400;
  --z-modal: 500;
}

/* Reduced motion preference */
@media (prefers-reduced-motion: reduce) {
  :root {
    --transition-fast: 0ms;
    --transition-normal: 0ms;
    --transition-slow: 0ms;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* ==========================================================================
   CSS Reset / Normalize
   ========================================================================== */

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

* {
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-normal);
  line-height: var(--line-height-normal);
  color: var(--color-text-primary);
  background-color: var(--color-background);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

button {
  cursor: pointer;
  background: none;
  border: none;
}

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

a:hover {
  color: var(--color-primary-dark);
}

ul,
ol {
  list-style: none;
}

/* ==========================================================================
   Typography
   ========================================================================== */

h1, h2, h3, h4, h5, h6 {
  font-weight: var(--font-weight-bold);
  line-height: var(--line-height-tight);
  letter-spacing: var(--letter-spacing-tight);
  color: var(--color-text-primary);
}

h1 {
  font-size: clamp(2.25rem, 5vw, var(--font-size-5xl));
}

h2 {
  font-size: clamp(1.875rem, 4vw, var(--font-size-4xl));
}

h3 {
  font-size: clamp(1.5rem, 3vw, var(--font-size-3xl));
}

h4 {
  font-size: var(--font-size-2xl);
}

h5 {
  font-size: var(--font-size-xl);
}

h6 {
  font-size: var(--font-size-lg);
}

p {
  margin-bottom: var(--space-4);
}

p:last-child {
  margin-bottom: 0;
}

strong, b {
  font-weight: var(--font-weight-semibold);
}

small {
  font-size: var(--font-size-sm);
}

.text-muted {
  color: var(--color-text-muted);
}

.text-secondary {
  color: var(--color-text-secondary);
}

.text-center {
  text-align: center;
}

.text-left {
  text-align: left;
}

.text-right {
  text-align: right;
}

/* Lead paragraph */
.lead {
  font-size: var(--font-size-xl);
  line-height: var(--line-height-relaxed);
  color: var(--color-text-secondary);
}

/* ==========================================================================
   Focus Styles (Accessibility)
   ========================================================================== */

:focus {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

:focus:not(:focus-visible) {
  outline: none;
}

:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* ==========================================================================
   Selection
   ========================================================================== */

::selection {
  background-color: var(--color-primary);
  color: var(--color-text-inverse);
}

/* ==========================================================================
   Skip Link (Accessibility)
   ========================================================================== */

.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-4);
  z-index: var(--z-modal);
  padding: var(--space-3) var(--space-4);
  background-color: var(--color-primary);
  color: var(--color-text-inverse);
  font-weight: var(--font-weight-medium);
  border-radius: var(--radius-md);
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: var(--space-4);
  outline-offset: 4px;
}

/* ==========================================================================
   Screen Reader Only
   ========================================================================== */

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}