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/* Base CSS Variables & Reset                                                         */
/* ──────────────────────────────────────────────────────────────────────────────── */

:root {
  /* Color Palette - Dark Theme Default */
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-tertiary: #334155;

  --text-primary: #f8fafc;
  --text-secondary: #e2e8f0;
  --text-muted: #94a3b8;

  --accent: #3b82f6;
  --accent-hover: #2563eb;

  --success: #22c55e;
  --warning: #f59e0b;
  --error: #ef4444;

  --border: #334155;

  /* Typography */
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  --font-mono: 'Fira Code', 'Monaco', 'Courier New', monospace;

  /* Spacing */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;

  /* Border Radius */
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --radius-xl: 12px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-normal: 250ms ease;

  /* Z-index layers */
  --z-base: 1;
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-modal: 1000;
  --z-toast: 1100;
}

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
}

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

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.25;
  margin-bottom: var(--space-md);
}

h1 { font-size: 1.875rem; }
h2 { font-size: 1.5rem; }
h3 { font-size: 1.25rem; }
h4 { font-size: 1.125rem; }
h5 { font-size: 1rem; }
h6 { font-size: 0.875rem; }

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

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

a:hover {
  color: var(--accent-hover);
}

/* Mobile heading adjustments */
@media (max-width: 640px) {
  h1 { font-size: 1.5rem; }
  h2 { font-size: 1.25rem; }
  h3 { font-size: 1.125rem; }
}

/* Scrollbar Styling */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}

::-webkit-scrollbar-thumb {
  background: var(--bg-tertiary);
  border-radius: var(--radius-sm);
}

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

/* Selection */
::selection {
  background: rgba(59, 130, 246, 0.3);
  color: var(--text-primary);
}

/* Focus Styles */
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* Touch-friendly tap target size (min 44x44px per WCAG) */
button,
a,
input,
select,
textarea {
  min-height: 44px;
  min-width: 44px;
}

/* App container */
#app {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Utility: Hide scrollbar but allow scroll */
.scrollbar-hide {
  -ms-overflow-style: none;
  scrollbar-width: none;
}

.scrollbar-hide::-webkit-scrollbar {
  display: none;
}

/* Utility: Text truncation */
.truncate {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

/* Utility: 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;
}