/* CSS Reset & Base Rules */
*, *::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(--text-base);
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Accessibility Skip Link */
.skip-link {
  position: absolute;
  top: -40px;
  left: 1rem;
  background: var(--color-primary);
  color: var(--color-text-inverse);
  padding: 0.5rem 1rem;
  z-index: 1000;
  text-decoration: none;
  font-weight: 600;
  border-radius: var(--radius-md);
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: 1rem;
  outline: 3px solid var(--color-text);
}

/* Typography Hierarchy */
h1, h2, h3, h4, h5, h6 {
  color: var(--color-text);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.02em;
}

h1 { font-size: var(--text-4xl); margin-bottom: var(--space-4); }
h2 { font-size: var(--text-3xl); margin-bottom: var(--space-4); }
h3 { font-size: var(--text-2xl); margin-bottom: var(--space-3); }
h4 { font-size: var(--text-xl); margin-bottom: var(--space-2); }
h5 { font-size: var(--text-lg); margin-bottom: var(--space-2); }
h6 { font-size: var(--text-base); margin-bottom: var(--space-2); }

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

p.lead {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  line-height: 1.6;
}

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

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

a:focus-visible, button:focus-visible, input:focus-visible, select:focus-visible, textarea:focus-visible {
  outline: var(--focus-ring);
  outline-offset: var(--focus-offset);
}

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

/* Layout Utilities */
.container {
  width: 100%;
  max-width: var(--container-xl);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--container-padding);
  padding-right: var(--container-padding);
}

.container-sm {
  max-width: var(--container-sm);
}

.container-md {
  max-width: var(--container-md);
}

.section {
  padding-top: var(--space-12);
  padding-bottom: var(--space-12);
}

.section-sm {
  padding-top: var(--space-8);
  padding-bottom: var(--space-8);
}

.main-content {
  flex: 1 0 auto;
}

/* Flex & Grid Helpers */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.justify-center { justify-content: center; }
.gap-1 { gap: var(--space-1); }
.gap-2 { gap: var(--space-2); }
.gap-3 { gap: var(--space-3); }
.gap-4 { gap: var(--space-4); }
.gap-6 { gap: var(--space-6); }
.gap-8 { gap: var(--space-8); }

.grid {
  display: grid;
  gap: var(--space-6);
}

.grid-cols-1 { grid-template-columns: repeat(1, minmax(0, 1fr)); }

@media (min-width: 640px) {
  .grid-cols-2-sm { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (min-width: 768px) {
  .grid-cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
}

@media (min-width: 1024px) {
  .grid-cols-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
}

/* Text Utilities */
.text-center { text-align: center; }
.text-right { text-align: right; }
.text-sm { font-size: var(--text-sm); }
.text-xs { font-size: var(--text-xs); }
.text-muted { color: var(--color-text-muted); }
.font-semibold { font-weight: 600; }
.font-bold { font-weight: 700; }

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

/* Motion Preferences */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}