/* ========================================
   BASE STYLES - CSS VARIABLES & RESET
   ======================================== */

:root {
  /* ========================================
     COLOR SYSTEM
     ======================================== */
  
  /* Primary Colors */
  --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --primary-color: #667eea;
  --secondary-color: #764ba2;
  --primary-light: #8a9eff;
  --primary-dark: #4c63d2;
  
  /* Semantic Colors */
  --success-color: #28a745;
  --warning-color: #ffc107;
  --danger-color: #dc3545;
  --info-color: #17a2b8;
  
  /* Neutral Colors */
  --white: #ffffff;
  --gray-50: #f8f9fa;
  --gray-100: #e9ecef;
  --gray-200: #dee2e6;
  --gray-300: #ced4da;
  --gray-400: #adb5bd;
  --gray-500: #6c757d;
  --gray-600: #495057;
  --gray-700: #343a40;
  --gray-800: #212529;
  --gray-900: #000000;
  
  /* Text Colors */
  --text-primary: var(--gray-800);
  --text-secondary: var(--gray-600);
  --text-muted: var(--gray-500);
  --text-light: var(--gray-400);
  
  /* Background Colors */
  --bg-primary: var(--white);
  --bg-secondary: var(--gray-50);
  --bg-tertiary: var(--gray-100);
  
  /* ========================================
     SPACING SCALE
     ======================================== */
  
  --spacing-xs: 0.25rem;    /* 4px */
  --spacing-sm: 0.5rem;      /* 8px */
  --spacing-md: 1rem;        /* 16px */
  --spacing-lg: 1.5rem;       /* 24px */
  --spacing-xl: 2rem;        /* 32px */
  --spacing-2xl: 3rem;       /* 48px */
  --spacing-3xl: 4rem;       /* 64px */
  
  /* ========================================
     TYPOGRAPHY SCALE
     ======================================== */
  
  --font-family-base: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-family-mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, Courier, monospace;
  
  --font-size-xs: 0.75rem;   /* 12px */
  --font-size-sm: 0.875rem;  /* 14px */
  --font-size-base: 1rem;    /* 16px */
  --font-size-lg: 1.125rem;  /* 18px */
  --font-size-xl: 1.25rem;   /* 20px */
  --font-size-2xl: 1.5rem;   /* 24px */
  --font-size-3xl: 1.875rem; /* 30px */
  --font-size-4xl: 2.25rem;  /* 36px */
  
  --font-weight-light: 300;
  --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: 1.75;
  
  /* ========================================
     Z-INDEX SCALE
     ======================================== */
  
  --z-dropdown: 1000;
  --z-sticky: 1020;
  --z-fixed: 1030;
  --z-modal-backdrop: 100000;
  --z-modal: 100001;
  --z-offcanvas: 100002;
  --z-tooltip: 100003;
  
  /* ========================================
     BORDER RADIUS
     ======================================== */
  
  --border-radius-sm: 0.25rem;  /* 4px */
  --border-radius-md: 0.375rem;  /* 6px */
  --border-radius-lg: 0.5rem;   /* 8px */
  --border-radius-xl: 0.75rem;  /* 12px */
  --border-radius-2xl: 1rem;     /* 16px */
  --border-radius-full: 9999px;
  
  /* ========================================
     SHADOWS
     ======================================== */
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  
  /* ========================================
     TRANSITIONS
     ======================================== */
  
  --transition-fast: 150ms ease-in-out;
  --transition-normal: 300ms ease-in-out;
  --transition-slow: 500ms ease-in-out;
  
  /* ========================================
     BREAKPOINTS (for reference)
     ======================================== */
  
  --breakpoint-sm: 576px;
  --breakpoint-md: 768px;
  --breakpoint-lg: 992px;
  --breakpoint-xl: 1200px;
  --breakpoint-2xl: 1400px;
}

/* ========================================
   RESET & BASE STYLES
   ======================================== */

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

html {
  font-size: 16px;
  line-height: var(--line-height-normal);
  -webkit-text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
  height: 100%;
}

body {
  margin: 0;
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-normal);
  line-height: var(--line-height-normal);
  color: var(--text-primary);
  background-color: var(--bg-secondary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* ========================================
   ACCESSIBILITY UTILITIES
   ======================================== */

/* Skip link for keyboard navigation */
.skip-link {
  position: absolute;
  top: -40px;
  left: var(--spacing-md);
  background: var(--primary-color);
  color: var(--white);
  padding: var(--spacing-sm) var(--spacing-md);
  text-decoration: none;
  border-radius: var(--border-radius-md);
  z-index: var(--z-modal);
  font-weight: var(--font-weight-medium);
  transition: var(--transition-fast);
}

.skip-link:focus {
  top: var(--spacing-sm);
}

/* Screen reader only content */
.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;
}

.sr-only-focusable:focus {
  position: static;
  width: auto;
  height: auto;
  padding: inherit;
  margin: inherit;
  overflow: visible;
  clip: auto;
  white-space: normal;
}

/* ========================================
   FOCUS STYLES
   ======================================== */

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

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

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

/* ========================================
   TYPOGRAPHY BASE
   ======================================== */

h1, h2, h3, h4, h5, h6 {
  margin-top: 0;
  margin-bottom: var(--spacing-md);
  font-weight: var(--font-weight-semibold);
  line-height: var(--line-height-tight);
  color: var(--text-primary);
}

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

p {
  margin-top: 0;
  margin-bottom: var(--spacing-md);
}

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

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

/* ========================================
   FORM ELEMENTS BASE
   ======================================== */

input,
button,
select,
textarea {
  font-family: inherit;
  font-size: inherit;
  line-height: inherit;
}

button {
  cursor: pointer;
}

/* ========================================
   IMAGE OPTIMIZATION
   ======================================== */

img {
  max-width: 100%;
  height: auto;
  vertical-align: middle;
}

/* ========================================
   CONTAINER BASE
   ======================================== */

.container-fluid {
  max-width: 100%;
  overflow-x: hidden;
}

@media (min-width: 768px) {
  .container-fluid {
    max-width: 100%;
    padding-left: var(--spacing-xl);
    padding-right: var(--spacing-xl);
  }
}

@media (min-width: 1200px) {
  .container-fluid {
    max-width: 1200px;
    margin: 0 auto;
  }
}