:root {
    /* Colors - Premium Analytics Theme */
    --color-bg-body: #f8f9fa;
    --color-bg-surface: #ffffff;
    --color-primary: #2563eb;
    --color-primary-dark: #1d4ed8;
    --color-text-main: #111827;
    --color-text-muted: #6b7280;
    --color-border: #e5e7eb;
    
    /* Spacing */
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 2rem;
    --spacing-xl: 4rem;
    
    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    
    /* Effects */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --radius-md: 0.5rem;
}

/* Reset & Base */
*, *::before, *::after { box-sizing: border-box; }
body {
    background-color: var(--color-bg-body);
    color: var(--color-text-main);
    font-family: var(--font-sans);
    line-height: 1.6;
    margin: 0;
    -webkit-font-smoothing: antialiased;
}

/* Typography */
h1, h2, h3, h4 { line-height: 1.2; font-weight: 700; margin: 0 0 var(--spacing-md); }
h1 { font-size: 2.5rem; letter-spacing: -0.02em; }
h2 { font-size: 2rem; letter-spacing: -0.01em; }
p { margin-bottom: var(--spacing-md); color: var(--color-text-muted); }

/* Layout Utilities */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

.grid {
    display: grid;
    gap: var(--spacing-lg);
}
.grid-2 { grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); }
.grid-3 { grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); }

/* Components */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    background-color: var(--color-primary);
    color: white;
    text-decoration: none;
    border-radius: var(--radius-md);
    font-weight: 600;
    transition: background-color 0.2s;
    border: none;
    cursor: pointer;
}
.btn:hover { background-color: var(--color-primary-dark); }
.btn-outline {
    background-color: transparent;
    border: 1px solid var(--color-border);
    color: var(--color-text-main);
}
.btn-outline:hover { border-color: var(--color-primary); color: var(--color-primary); }

.card {
    background: var(--color-bg-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-sm);
    transition: transform 0.2s, box-shadow 0.2s;
}
.card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

/* Header */
header {
    background: var(--color-bg-surface);
    border-bottom: 1px solid var(--color-border);
    padding: var(--spacing-md) 0;
    position: sticky;
    top: 0;
    z-index: 100;
}
.nav-flex {
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.brand { font-weight: 700; font-size: 1.25rem; text-decoration: none; color: var(--color-text-main); }
.nav-link { margin-left: var(--spacing-lg); text-decoration: none; color: var(--color-text-muted); font-weight: 500; }
.nav-link:hover, .nav-link.active { color: var(--color-primary); }

/* Footer */
footer {
    background: var(--color-bg-surface);
    border-top: 1px solid var(--color-border);
    padding: var(--spacing-xl) 0;
    margin-top: var(--spacing-xl);
    text-align: center;
}