/* ==========================================================================
   Base CSS - Core styles and variables
   ========================================================================== */

/* ==========================================================================
   Custom Properties (Variables)
   ========================================================================== */

:root {
  /* Color Scheme */
  --color-primary: #007bff;
  --color-secondary: #6c757d;
  --color-success: #28a745;
  --color-danger: #dc3545;
  --color-warning: #ffc107;
  --color-info: #17a2b8;
  --color-light: #f8f9fa;
  --color-dark: #343a40;
  
  /* Neutral Colors */
  --color-white: #ffffff;
  --color-gray-100: #f8f9fa;
  --color-gray-200: #e9ecef;
  --color-gray-300: #dee2e6;
  --color-gray-400: #ced4da;
  --color-gray-500: #adb5bd;
  --color-gray-600: #6c757d;
  --color-gray-700: #495057;
  --color-gray-800: #343a40;
  --color-gray-900: #212529;
  --color-black: #000000;

  /* Typography Scale (8pt grid) */
  --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 Weights */
  --font-weight-light: 300;
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;

  /* Line Heights */
  --line-height-tight: 1.25;
  --line-height-snug: 1.375;
  --line-height-normal: 1.5;
  --line-height-relaxed: 1.625;
  --line-height-loose: 2;

  /* Spacing System (8pt grid) */
  --spacing-1: 0.25rem;   /* 4px */
  --spacing-2: 0.5rem;    /* 8px */
  --spacing-3: 0.75rem;   /* 12px */
  --spacing-4: 1rem;      /* 16px */
  --spacing-5: 1.5rem;    /* 24px */
  --spacing-6: 2rem;      /* 32px */
  --spacing-8: 3rem;      /* 48px */
  --spacing-10: 4rem;     /* 64px */
  --spacing-12: 5rem;     /* 80px */
  
  /* Breakpoints */
  --breakpoint-xs: 0;
  --breakpoint-sm: 576px;
  --breakpoint-md: 768px;
  --breakpoint-lg: 992px;
  --breakpoint-xl: 1200px;
  --breakpoint-xxl: 1400px;

  /* Border Radius */
  --border-radius-sm: 0.25rem;
  --border-radius-md: 0.375rem;
  --border-radius-lg: 0.5rem;
  --border-radius-full: 9999px;
}

/* ==========================================================================
   Reset/Normalize
   ========================================================================== */

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-normal);
  line-height: var(--line-height-normal);
  color: var(--color-gray-900);
  background-color: var(--color-white);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ==========================================================================
   Typography
   ========================================================================== */

h1, h2, h3, h4, h5, h6 {
  margin-top: 0;
  margin-bottom: var(--spacing-4);
  font-weight: var(--font-weight-bold);
  line-height: var(--line-height-tight);
}

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-4);
}

a {
  color: var(--color-primary);
  text-decoration: none;
  background-color: transparent;
}

a:hover {
  color: #0056b3;
  text-decoration: underline;
}

/* ==========================================================================
   Common Elements
   ========================================================================== */

/* Buttons */
.btn {
  display: inline-block;
  padding: var(--spacing-2) var(--spacing-4);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-medium);
  line-height: var(--line-height-normal);
  text-align: center;
  text-decoration: none;
  vertical-align: middle;
  cursor: pointer;
  user-select: none;
  border: 1px solid transparent;
  border-radius: var(--border-radius-md);
  transition: color 0.15s ease-in-out, background-color 0.15s ease-in-out, border-color 0.15s ease-in-out;
}

.btn-primary {
  color: var(--color-white);
  background-color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn-primary:hover {
  color: var(--color-white);
  background-color: #0069d9;
  border-color: #0062cc;
}

/* Form Elements */
input,
select,
textarea {
  display: block;
  width: 100%;
  padding: var(--spacing-2) var(--spacing-3);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-normal);
  line-height: var(--line-height-normal);
  color: var(--color-gray-900);
  background-color: var(--color-white);
  border: 1px solid var(--color-gray-400);
  border-radius: var(--border-radius-md);
  transition: border-color 0.15s ease-in-out, box-shadow 0.15s ease-in-out;
}

input:focus,
select:focus,
textarea:focus {
  border-color: #80bdff;
  outline: 0;
  box-shadow: 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}

/* Lists */
ul, ol {
  margin-top: 0;
  margin-bottom: var(--spacing-4);
  padding-left: var(--spacing-5);
}

/* ==========================================================================
   Layout Utilities
   ========================================================================== */

.container {
  width: 100%;
  padding-right: var(--spacing-4);
  padding-left: var(--spacing-4);
  margin-right: auto;
  margin-left: auto;
}

@media (min-width: 576px) {
  .container {
    max-width: 540px;
  }
}

@media (min-width: 768px) {
  .container {
    max-width: 720px;
  }
}

@media (min-width: 992px) {
  .container {
    max-width: 960px;
  }
}

@media (min-width: 1200px) {
  .container {
    max-width: 1140px;
  }
}

/* Spacing Utilities */
.m-0 { margin: 0 !important; }
.mt-0 { margin-top: 0 !important; }
.mr-0 { margin-right: 0 !important; }
.mb-0 { margin-bottom: 0 !important; }
.ml-0 { margin-left: 0 !important; }

.p-0 { padding: 0 !important; }
.pt-0 { padding-top: 0 !important; }
.pr-0 { padding-right: 0 !important; }
.pb-0 { padding-bottom: 0 !important; }
.pl-0 { padding-left: 0 !important; }

/* Display Utilities */
.d-none { display: none !important; }
.d-inline { display: inline !important; }
.d-inline-block { display: inline-block !important; }
.d-block { display: block !important; }
.d-flex { display: flex !important; }

/* Flex Utilities */
.flex-row { flex-direction: row !important; }
.flex-column { flex-direction: column !important; }
.justify-content-start { justify-content: flex-start !important; }
.justify-content-center { justify-content: center !important; }
.justify-content-end { justify-content: flex-end !important; }
.align-items-start { align-items: flex-start !important; }
.align-items-center { align-items: center !important; }
.align-items-end { align-items: flex-end !important; }