/* ============================================
   BASE: Variables, resets, scrollbar, typography
   Guitar Club - Student Materials
   ============================================ */

:root {
  /* Layout dimensions */
  --sidebar-width: 240px;
  --content-max: 900px;
  --tab-max: 720px;
  --video-max-height: 400px;
  
  /* Spacing scale (8pt grid) */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  
  /* Theme colors */
  --bg-primary: #0d1117;
  --bg-secondary: #161b22;
  --bg-tertiary: #21262d;
  --text-primary: #e6edf3;
  --text-secondary: #7d8590;
  --text-muted: #484f58;
  --accent: #58a6ff;
  --accent-green: #3fb950;
  --accent-orange: #ffa657;
  --border: #30363d;
  
  /* Typography */
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', 'Consolas', 'Courier New', monospace;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  line-height: 1.5;
}

/* ============================================
   STARRY SPACE BACKGROUND
   ============================================ */
body::before,
body::after {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: -1;
}

/* Star layer 1 - small distant stars */
body::before {
  background-image: 
    radial-gradient(1px 1px at 20px 30px, white, transparent),
    radial-gradient(1px 1px at 40px 70px, rgba(255,255,255,0.8), transparent),
    radial-gradient(1px 1px at 50px 160px, rgba(255,255,255,0.6), transparent),
    radial-gradient(1px 1px at 90px 40px, white, transparent),
    radial-gradient(1px 1px at 130px 80px, rgba(255,255,255,0.7), transparent),
    radial-gradient(1px 1px at 160px 120px, white, transparent),
    radial-gradient(1px 1px at 200px 50px, rgba(255,255,255,0.5), transparent),
    radial-gradient(1px 1px at 220px 150px, white, transparent),
    radial-gradient(1px 1px at 250px 90px, rgba(255,255,255,0.8), transparent),
    radial-gradient(1px 1px at 280px 30px, white, transparent),
    radial-gradient(1px 1px at 310px 180px, rgba(255,255,255,0.6), transparent),
    radial-gradient(1px 1px at 350px 60px, white, transparent),
    radial-gradient(1px 1px at 380px 140px, rgba(255,255,255,0.9), transparent),
    radial-gradient(1px 1px at 420px 100px, white, transparent),
    radial-gradient(1px 1px at 450px 20px, rgba(255,255,255,0.7), transparent),
    radial-gradient(1px 1px at 480px 170px, white, transparent),
    radial-gradient(1px 1px at 510px 45px, rgba(255,255,255,0.5), transparent),
    radial-gradient(1px 1px at 540px 130px, white, transparent),
    radial-gradient(1px 1px at 580px 75px, rgba(255,255,255,0.8), transparent),
    radial-gradient(1px 1px at 620px 165px, white, transparent);
  background-repeat: repeat;
  background-size: 650px 200px;
  animation: twinkle 4s ease-in-out infinite alternate;
}

/* Star layer 2 - brighter closer stars */
body::after {
  background-image: 
    radial-gradient(2px 2px at 100px 50px, rgba(255,255,255,0.9), transparent),
    radial-gradient(2px 2px at 300px 120px, rgba(200,220,255,0.8), transparent),
    radial-gradient(1.5px 1.5px at 180px 180px, rgba(255,255,200,0.9), transparent),
    radial-gradient(2px 2px at 500px 80px, rgba(255,255,255,0.7), transparent),
    radial-gradient(1.5px 1.5px at 650px 160px, rgba(200,200,255,0.8), transparent),
    radial-gradient(2px 2px at 400px 200px, white, transparent),
    radial-gradient(1.5px 1.5px at 50px 140px, rgba(255,220,200,0.9), transparent),
    radial-gradient(2px 2px at 750px 40px, rgba(255,255,255,0.8), transparent);
  background-repeat: repeat;
  background-size: 800px 250px;
  animation: twinkle 6s ease-in-out infinite alternate-reverse;
}

@keyframes twinkle {
  0% { opacity: 0.5; }
  50% { opacity: 0.8; }
  100% { opacity: 1; }
}

/* Offset for sticky elements when using anchor links */
[id] {
  scroll-margin-top: 60px;
}

/* Links */
a {
  color: var(--accent);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

/* ============================================
   SCROLLBAR: Themed for dark mode
   ============================================ */

/* Webkit browsers (Chrome, Safari, Edge) */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-secondary);
}

::-webkit-scrollbar-corner {
  background: transparent;
}

/* Standard properties (Firefox, Chrome 121+) */
@supports not selector(::-webkit-scrollbar) {
  * {
    scrollbar-width: thin;
    scrollbar-color: var(--border) transparent;
  }
}

/* ============================================
   ALIASES: song.css compatibility layer
   Maps song page variable names → hub tokens
   Remove after song.css is fully migrated
   ============================================ */
:root {
  --bg-body: var(--bg-primary);
  --bg-surface: var(--bg-secondary);
  --bg-surface-hover: var(--bg-tertiary);
  --bg-accent-subtle: rgba(88, 166, 255, 0.1);
  --border-color: var(--border);
  --border-highlight: var(--text-muted);
  --accent-color: var(--accent);
  --accent-hover: var(--accent);
  --container-width: var(--content-max);
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 16px;
}