/* Design Tokens & CSS Variables */
:root {
  /* Color Palette - Dark Premium Theme default with high contrast */
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: #1e293b;
  --bg-hover: #334155;
  
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  
  --accent-primary: #38bdf8;
  --accent-secondary: #818cf8;
  --accent-glow: rgba(56, 189, 248, 0.15);
  
  --border-color: #334155;
  --focus-ring: #38bdf8;

  /* Typography */
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --line-height-base: 1.6;
  --line-height-heading: 1.2;

  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2.5rem;
  --spacing-xl: 4rem;

  /* Border Radius */
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
}

/* CSS Reset & Accessibility Baseline */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 100%;
}

body {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-family);
  line-height: var(--line-height-base);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
}

/* Accessibility Keyboard Focus Styles (WCAG 2.1 AA) */
a:focus-visible,
button:focus-visible,
input:focus-visible,
textarea:focus-visible {
  outline: 3px solid var(--focus-ring);
  outline-offset: 4px;
  border-radius: var(--radius-sm);
}

/* Typography Base */
h1, h2, h3, h4, h5, h6 {
  line-height: var(--line-height-heading);
  color: var(--text-primary);
  font-weight: 700;
}

h1 { font-size: clamp(2rem, 5vw, 3.5rem); }
h2 { font-size: clamp(1.5rem, 3vw, 2.5rem); }
h3 { font-size: clamp(1.2rem, 2vw, 1.75rem); }

p {
  color: var(--text-secondary);
  font-size: 1.05rem;
}

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

a:hover {
  text-decoration: underline;
}

/* Skip to Content Link (A11y Requirement) */
.skip-link {
  position: absolute;
  top: -100px;
  left: 1rem;
  background: var(--accent-primary);
  color: #0f172a;
  padding: 0.75rem 1.25rem;
  font-weight: bold;
  z-index: 9999;
  border-radius: var(--radius-sm);
  transition: top 0.2s ease;
}

.skip-link:focus {
  top: 1rem;
}