/* ============================================
   BASE CSS - Reset, Variables, Typography
   ============================================ */

/* CSS Reset */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* CSS Custom Properties (Variables) */
:root {
    /* Primary Colors */
    --primary-color: #2563eb;
    --primary-dark: #1e40af;
    --primary-light: #3b82f6;
    
    /* Secondary Colors */
    --secondary-color: #0f172a;
    --secondary-light: #1e293b;
    
    /* Accent Colors */
    --accent-color: #f59e0b;
    --accent-dark: #d97706;
    --accent-light: #fbbf24;
    
    /* Status Colors */
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --info-color: #3b82f6;
    
    /* Neutral Colors */
    --light-color: #f3f4f6;
    --dark-color: #1f2937;
    --border-color: #e5e7eb;
    --text-color: #1f2937;
    --text-muted: #6b7280;
    --white: #ffffff;
    --black: #000000;
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #2563eb 0%, #1e40af 50%, #0f172a 100%);
    --gradient-accent: linear-gradient(135deg, #f59e0b 0%, #f97316 100%);
    --gradient-light: linear-gradient(135deg, #dbeafe 0%, #fef3c7 100%);
    --gradient-dark: linear-gradient(135deg, #0f172a 0%, #1e40af 100%);
    
    /* Shadows */
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 10px 30px rgba(37, 99, 235, 0.15);
    --shadow-lg: 0 30px 60px rgba(37, 99, 235, 0.25);
    --shadow-xl: 0 40px 80px rgba(37, 99, 235, 0.35);
    
    /* Border Radius */
    --radius-sm: 5px;
    --radius-md: 10px;
    --radius-lg: 15px;
    --radius-xl: 25px;
    --radius-full: 50%;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --spacing-3xl: 4rem;
    
    /* Font Sizes */
    --text-xs: 0.75rem;
    --text-sm: 0.875rem;
    --text-base: 1rem;
    --text-lg: 1.125rem;
    --text-xl: 1.25rem;
    --text-2xl: 1.5rem;
    --text-3xl: 2rem;
    --text-4xl: 2.5rem;
    --text-5xl: 3rem;
    
    /* Font Weights */
    --font-light: 300;
    --font-normal: 400;
    --font-medium: 500;
    --font-semibold: 600;
    --font-bold: 700;
    --font-extrabold: 800;
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
    --transition-bounce: 0.4s cubic-bezier(0.23, 1, 0.320, 1);
    
    /* Z-Index Scale */
    --z-dropdown: 100;
    --z-sticky: 500;
    --z-fixed: 1000;
    --z-modal: 2000;
    --z-tooltip: 3000;
}

/* Base Typography */
html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    color: var(--text-color);
    line-height: 1.6;
    background-color: var(--white);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Headings */
h1, h2, h3, h4, h5, h6 {
    font-weight: var(--font-bold);
    line-height: 1.2;
    color: var(--secondary-color);
}

h1 { font-size: var(--text-5xl); }
h2 { font-size: var(--text-4xl); }
h3 { font-size: var(--text-3xl); }
h4 { font-size: var(--text-2xl); }
h5 { font-size: var(--text-xl); }
h6 { font-size: var(--text-lg); }

/* Paragraphs */
p {
    margin-bottom: var(--spacing-md);
    color: var(--text-muted);
}

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

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

/* Lists */
ul, ol {
    list-style: none;
}

/* Images */
img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* Forms */
input, textarea, select, button {
    font-family: inherit;
    font-size: inherit;
}

/* Selection */
::selection {
    background-color: var(--primary-color);
    color: var(--white);
}

/* Focus Styles for Accessibility */
:focus {
    outline: 3px solid var(--primary-light);
    outline-offset: 2px;
}

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

:focus-visible {
    outline: 3px solid var(--primary-light);
    outline-offset: 2px;
}

/* 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;
}

/* Skip Link for Accessibility */
.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--primary-color);
    color: var(--white);
    padding: var(--spacing-sm) var(--spacing-md);
    z-index: var(--z-tooltip);
    transition: top var(--transition-fast);
}

.skip-link:focus {
    top: 0;
}