:root {
    --primary-color: #2563eb;
    --secondary-color: #7c3aed;
    --success-color: #16a34a;
    --warning-color: #ea580c;
    --danger-color: #dc2626;
    --info-color: #0891b2;
    
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --text-muted: #9ca3af;
    
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-accent: #f1f5f9;
    
    --border-color: #e5e7eb;
    --border-radius: 0.75rem;
    --box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --box-shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    
    --font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --transition: all 0.3s ease;
}

/* Dark Theme */
[data-theme="dark"] {
    --text-primary: #f9fafb;
    --text-secondary: #d1d5db;
    --text-muted: #9ca3af;
    --bg-primary: #111827;
    --bg-secondary: #1f2937;
    --bg-accent: #374151;
    --border-color: #374151;
}

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

body {
    font-family: var(--font-family);
    background: var(--bg-secondary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: var(--transition);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1rem;
}

/* Header */
.header {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 1rem 0;
    box-shadow: var(--box-shadow);
}

.header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.75rem;
    font-weight: bold;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.theme-btn {
    background: rgba(255, 255, 255, 0.2);
    border: none;
    color: white;
    padding: 0.5rem;
    border-radius: 50%;
    cursor: pointer;
    transition: var(--transition);
}

.theme-btn:hover {
    background: rgba(255, 255, 255, 0.3);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 1rem 2rem;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
}

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

.btn-primary:hover {
    background: #1d4ed8;
    transform: translateY(-2px);
    box-shadow: var(--box-shadow-lg);
}

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

.btn-success:hover {
    background: #15803d;
    transform: translateY(-2px);
    box-shadow: var(--box-shadow-lg);
}

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

.btn-warning:hover {
    background: #c2410c;
    transform: translateY(-2px);
    box-shadow: var(--box-shadow-lg);
}

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

.btn-danger:hover {
    background: #b91c1c;
    transform: translateY(-2px);
    box-shadow: var(--box-shadow-lg);
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

/* Footer */
footer {
    text-align: center;
    padding: 2rem;
    background: var(--bg-primary);
    margin-top: 2rem;
    border-top: 1px solid var(--border-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .header .container {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
        padding: 0 1rem;
    }
    
    .logo {
        font-size: 1.5rem;
    }
    
    .btn {
        padding: 0.75rem 1.5rem;
    }
}