/* ==========================================
   BrainBench Pro - Design System
   ========================================== */

/* CSS Variables for Consistent Design */
:root {
    /* Primary Colors */
    --primary-purple: #764ba2;
    --primary-purple-light: #667eea;
    --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    
    /* Accent Colors for Categories */
    --accent-teal: #00d4aa;
    --accent-orange: #ffa726;
    --accent-pink: #e91e63;
    --accent-blue: #5e72e4;
    --accent-green: #51cf66;
    --accent-purple: #8b5cf6;
    
    /* Neutral Colors */
    --white: #ffffff;
    --gray-50: #f8f9fa;
    --gray-100: #f1f3f5;
    --gray-200: #e9ecef;
    --gray-300: #dee2e6;
    --gray-400: #ced4da;
    --gray-500: #adb5bd;
    --gray-600: #6c757d;
    --gray-700: #495057;
    --gray-800: #343a40;
    --gray-900: #212529;
    
    /* Semantic Colors */
    --success: #51cf66;
    --warning: #ffd43b;
    --error: #ff6b6b;
    --info: #4dabf7;
    
    /* Shadows */
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.15);
    --shadow-lg: 0 10px 30px rgba(0,0,0,0.2);
    --shadow-xl: 0 20px 60px rgba(0,0,0,0.3);
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --radius-full: 9999px;
    
    /* Spacing */
    --space-xs: 8px;
    --space-sm: 12px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;
    
    /* Typography */
    --font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;
    
    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-base: 0.3s ease;
    --transition-slow: 0.5s ease;
    
    /* Mobile Breakpoints */
    --breakpoint-sm: 640px;
    --breakpoint-md: 768px;
    --breakpoint-lg: 1024px;
    --breakpoint-xl: 1280px;
}

/* ==========================================
   Global Styles
   ========================================== */

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

body {
    font-family: var(--font-family);
    background: var(--gradient-primary);
    min-height: 100vh;
    color: var(--gray-900);
    line-height: 1.6;
}

/* ==========================================
   Header Navigation
   ========================================== */

.site-header {
    background: var(--primary-purple);
    padding: 1rem 2rem;
    box-shadow: var(--shadow-md);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: var(--font-size-xl);
    font-weight: bold;
    color: var(--white);
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.nav-menu {
    list-style: none;
    display: flex;
    gap: 2rem;
    align-items: center;
}

.nav-menu a {
    color: var(--white);
    text-decoration: none;
    font-weight: 500;
    font-size: var(--font-size-base);
    transition: opacity var(--transition-base);
    position: relative;
}

.nav-menu a:hover {
    opacity: 0.8;
}

.nav-menu a.active::after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--white);
    border-radius: var(--radius-full);
}

/* Hamburger Menu */
.hamburger {
    display: none;
    flex-direction: column;
    gap: 4px;
    cursor: pointer;
    background: none;
    border: none;
    padding: 8px;
}

.hamburger span {
    display: block;
    width: 24px;
    height: 3px;
    background: var(--white);
    border-radius: var(--radius-full);
    transition: var(--transition-base);
}

.hamburger.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}

.hamburger.active span:nth-child(2) {
    opacity: 0;
}

.hamburger.active span:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -6px);
}

/* ==========================================
   Footer
   ========================================== */

.site-footer {
    background: rgba(0, 0, 0, 0.2);
    color: var(--white);
    text-align: center;
    padding: 2rem 1rem;
    margin-top: auto;
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: 2rem;
    flex-wrap: wrap;
    margin-top: 1rem;
}

.footer-links a {
    color: var(--white);
    text-decoration: none;
    font-size: var(--font-size-sm);
    transition: opacity var(--transition-base);
}

.footer-links a:hover {
    opacity: 0.8;
}

/* ==========================================
   Buttons
   ========================================== */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 12px 32px;
    border: none;
    border-radius: var(--radius-full);
    font-size: var(--font-size-base);
    font-weight: 600;
    cursor: pointer;
    text-decoration: none;
    transition: all var(--transition-base);
    min-height: 44px;
    font-family: inherit;
}

.btn-primary {
    background: var(--gradient-primary);
    color: var(--white);
    box-shadow: var(--shadow-md);
}

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

.btn-primary:active {
    transform: translateY(0);
}

.btn-secondary {
    background: var(--white);
    color: var(--primary-purple);
    box-shadow: var(--shadow-sm);
}

.btn-secondary:hover {
    background: var(--gray-50);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-outline {
    background: transparent;
    color: var(--white);
    border: 2px solid var(--white);
}

.btn-outline:hover {
    background: rgba(255, 255, 255, 0.1);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none !important;
}

.btn-lg {
    padding: 16px 48px;
    font-size: var(--font-size-lg);
}

.btn-sm {
    padding: 8px 20px;
    font-size: var(--font-size-sm);
    min-height: 36px;
}

/* ==========================================
   Cards
   ========================================== */

.card {
    background: var(--white);
    border-radius: var(--radius-xl);
    padding: var(--space-2xl);
    box-shadow: var(--shadow-xl);
    width: 100%;
}

.card-body {
    padding: var(--space-lg);
}

.card-title {
    font-size: var(--font-size-2xl);
    font-weight: bold;
    color: var(--gray-900);
    margin-bottom: var(--space-md);
}

/* ==========================================
   Badges
   ========================================== */

.badge {
    display: inline-block;
    padding: 6px 16px;
    border-radius: var(--radius-full);
    font-size: var(--font-size-sm);
    font-weight: 600;
}

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

.badge-medium {
    background: var(--warning);
    color: var(--gray-900);
}

.badge-hard {
    background: var(--error);
    color: var(--white);
}

/* ==========================================
   Mobile Responsive
   ========================================== */

@media (max-width: 768px) {
    .hamburger {
        display: flex;
    }
    
    .nav-menu {
        position: fixed;
        top: 64px;
        left: 0;
        right: 0;
        background: var(--primary-purple);
        flex-direction: column;
        padding: 2rem;
        gap: 1.5rem;
        transform: translateX(-100%);
        transition: transform var(--transition-base);
        box-shadow: var(--shadow-lg);
    }
    
    .nav-menu.active {
        transform: translateX(0);
    }
    
    .nav-menu a.active::after {
        display: none;
    }
    
    .card {
        padding: var(--space-lg);
    }
    
    .btn {
        width: 100%;
    }
    
    .footer-links {
        gap: 1rem;
    }
}

@media (max-width: 480px) {
    .site-header {
        padding: 1rem;
    }
    
    .logo {
        font-size: var(--font-size-lg);
    }
    
    .card {
        padding: var(--space-md);
    }
}

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

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

.flex {
    display: flex;
}

.flex-col {
    flex-direction: column;
}

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

.justify-center {
    justify-content: center;
}

.gap-sm {
    gap: var(--space-sm);
}

.gap-md {
    gap: var(--space-md);
}

.gap-lg {
    gap: var(--space-lg);
}

.mt-sm {
    margin-top: var(--space-sm);
}

.mt-md {
    margin-top: var(--space-md);
}

.mt-lg {
    margin-top: var(--space-lg);
}

.mb-sm {
    margin-bottom: var(--space-sm);
}

.mb-md {
    margin-bottom: var(--space-md);
}

.mb-lg {
    margin-bottom: var(--space-lg);
}

/* ==========================================
   Common Page Layout Styles
   ========================================== */

.page-content {
    flex: 1;
    padding: 40px 20px;
}

.content-card {
    max-width: 800px;
    margin: 0 auto;
}

.content-card h1 {
    color: var(--primary-purple);
    margin-bottom: 1.5rem;
    font-size: 2rem;
}

.content-card h2 {
    color: var(--primary-purple-light);
    margin-top: 2rem;
    margin-bottom: 1rem;
    font-size: 1.5rem;
}

.content-card p {
    margin-bottom: 1rem;
    color: var(--gray-700);
}

.content-card ul, .content-card ol {
    margin-bottom: 1rem;
    padding-left: 1.5rem;
    color: var(--gray-700);
}

.content-card li {
    margin-bottom: 0.5rem;
}