/* ==========================================================================
   CSS Variables & Theme Tokens
   ========================================================================== */
:root {
    /* Colors - Premium Dark Theme (Default) */
    --bg-primary: #020617; /* Deep Slate */
    --bg-primary-rgb: 2, 6, 23;
    --bg-secondary: #0f172a; /* Slate 900 */
    --bg-secondary-rgb: 15, 23, 42;
    --bg-tertiary: #1e293b; /* Slate 800 */
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-tertiary: #94a3b8;
    
    /* Branding Colors */
    --brand-primary: #3b82f6; /* Blue */
    --brand-primary-hover: #2563eb;
    --brand-secondary: #8b5cf6; /* Purple */
    --brand-accent: #0ea5e9; /* Light Blue */
    
    /* Semantic Colors */
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --info: #3b82f6;
    
    /* Borders & Shadows */
    --border-color: #1e293b;
    --border-color-hover: #334155;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.5);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.5), 0 2px 4px -2px rgb(0 0 0 / 0.5);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5), 0 4px 6px -4px rgb(0 0 0 / 0.5);
    --shadow-glow: 0 0 20px rgba(59, 130, 246, 0.25);
    --shadow-glow-strong: 0 0 30px rgba(59, 130, 246, 0.4);
    
    /* Geometry */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    --radius-full: 9999px;
    
    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-normal: 300ms ease;
}

/* Light Theme Variables (Override) */
body.light-theme {
    --bg-primary: #f8fafc;
    --bg-primary-rgb: 248, 250, 252;
    --bg-secondary: #ffffff;
    --bg-secondary-rgb: 255, 255, 255;
    --bg-tertiary: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-tertiary: #64748b;
    
    --border-color: #e2e8f0;
    --border-color-hover: #cbd5e1;
    
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.08), 0 2px 4px -2px rgb(0 0 0 / 0.04);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.08), 0 4px 6px -4px rgb(0 0 0 / 0.04);
    --shadow-glow: 0 0 20px rgba(59, 130, 246, 0.15);
}

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

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

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color var(--transition-normal), color var(--transition-normal);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
}

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

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

ul {
    list-style: none;
}

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

/* Typography Scale */
h1, h2, h3, h4, h5, h6 {
    color: var(--text-primary);
    line-height: 1.2;
    font-weight: 700;
}

h1 { font-size: clamp(2.5rem, 5vw, 4.5rem); letter-spacing: -0.02em; }
h2 { font-size: clamp(2rem, 3vw, 2.5rem); letter-spacing: -0.01em; }
h3 { font-size: clamp(1.5rem, 2vw, 1.75rem); }
p { font-size: 1.125rem; line-height: 1.7; margin-bottom: 1rem; color: var(--text-secondary); }

/* ==========================================================================
   Layout structure
   ========================================================================== */
.container {
    width: 100%;
    max-width: 1536px; /* Expanded for premium feel */
    margin: 0 auto;
    padding: 0 1.5rem;
}

.section {
    padding: 6rem 0;
}

.bg-alt {
    background-color: var(--bg-secondary);
}

.section-header {
    text-align: center;
    margin-bottom: 4rem;
}

.section-title {
    margin-bottom: 1rem;
}

.section-desc {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 700px;
    margin: 0 auto;
}

.text-center {
    text-align: center;
}

/* Typography Utilities */
.gradient-text {
    background: linear-gradient(135deg, var(--brand-primary) 0%, var(--brand-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    color: transparent;
}