:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #e0e7ff;
    --success: #10b981;
    --error: #ef4444;
    --warning: #f59e0b;
    --info: #3b82f6;
    --purple: #8b5cf6;
    --pink: #ec4899;
    --dark: #0f172a;
    --gray: #64748b;
    --gray-light: #f1f5f9;
    --white: #ffffff;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --border-radius: 12px;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
    color: var(--dark);
    line-height: 1.6;
}

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

/* Profile Section */
.profile-section {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-left: auto;
}

.search-container {
    position: relative;
}

.search-input {
    padding: 8px 40px 8px 12px;
    border: 2px solid #e2e8f0;
    border-radius: 20px;
    outline: none;
    transition: all 0.3s ease;
    width: 200px;
}

.search-input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 0.2rem rgba(99, 102, 241, 0.15);
    width: 250px;
}

.search-icon {
    position: absolute;
    right: 12px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--gray);
}

.notification-btn, .profile-btn {
    background: none;
    border: none;
    padding: 8px;
    border-radius: 50%;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
}

.notification-btn:hover, .profile-btn:hover {
    background: var(--primary-light);
    color: var(--primary);
}

.notification-badge {
    position: absolute;
    top: 2px;
    right: 2px;
    background: var(--error);
    color: white;
    border-radius: 50%;
    padding: 2px 6px;
    font-size: 0.75rem;
    min-width: 18px;
    text-align: center;
}

/* Main Content */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

.hero-section {
    text-align: center;
    padding: 1rem 0;
}

.hero-title {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--dark);
    margin-bottom: 1rem;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--gray);
    margin-bottom: 2rem;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.hero-image {
    background: white;
    border-radius: var(--border-radius);
    padding: 2rem;
    box-shadow: var(--shadow-lg);
    margin: 2rem 0;
    display: inline-block;
}

.hero-image img {
    max-width: 100%;
    height: auto;
    border-radius: var(--border-radius);
}

/* Features Grid */
.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin: 3rem 0;
}

.feature {
    background: white;
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    text-align: center;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    position: relative;
    overflow: hidden;
}

.feature::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(99, 102, 241, 0.1), transparent);
    transition: left 0.5s;
}

.feature:hover::before {
    left: 100%;
}

.feature:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.feature-icon {
    width: 60px;
    height: 60px;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 1rem;
    color: white;
    font-size: 1.5rem;
    position: relative;
    z-index: 1;
}

.feature h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--dark);
    position: relative;
    z-index: 1;
}

.feature p {
    color: var(--gray);
    font-size: 0.9rem;
    position: relative;
    z-index: 1;
}

.section-title {
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 1rem;
    color: var(--dark);
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 4px;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    border-radius: 2px;
}

.section-description {
    text-align: center;
    color: var(--gray);
    margin-bottom: 3rem;
    font-size: 1.1rem;
}

.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
    margin-bottom: 3rem;
}

.topic-card {
    background: white;
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
    cursor: pointer;
    border: 2px solid transparent;
    position: relative;
    overflow: hidden;
}

.topic-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.topic-card:hover::before {
    left: 100%;
}

.topic-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary);
}

.topic-card h4 {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--dark);
    position: relative;
    z-index: 1;
}

.topic-card p {
    color: var(--gray);
    font-size: 0.9rem;
    margin-bottom: 1rem;
    position: relative;
    z-index: 1;
}

.topic-link {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--primary);
    text-decoration: none;
    font-weight: 500;
    font-size: 0.9rem;
    transition: color 0.3s ease;
    position: relative;
    z-index: 1;
}

.topic-link:hover {
    color: var(--primary-dark);
}

.topic-link i {
    transition: transform 0.3s ease;
}

.topic-card:hover .topic-link i {
    transform: translateX(5px);
}

/* Category Colors - Grammar/Verbal/Basic */
.grammar .topic-card:hover,
.verbal .topic-card:hover,
.basic .topic-card:hover {
    border-color: var(--success);
}

.grammar .topic-link,
.verbal .topic-link,
.basic .topic-link {
    color: var(--success);
}

.basic .section-title::after {
    background: linear-gradient(135deg, var(--success), #059669);
}

/* Category Colors - Vocabulary/Non-verbal/Advanced */
.vocabulary .topic-card:hover,
.non-verbal .topic-card:hover,
.advanced .topic-card:hover {
    border-color: var(--warning);
}

.vocabulary .topic-link,
.non-verbal .topic-link,
.advanced .topic-link {
    color: var(--warning);
}

.advanced .section-title::after {
    background: linear-gradient(135deg, var(--warning), #d97706);
}

/* Category Colors - Comprehension/Analytical */
.comprehension .topic-card:hover,
.analytical .topic-card:hover {
    border-color: var(--info);
}

.comprehension .topic-link,
.analytical .topic-link {
    color: var(--info);
}

/* Category Colors - Algebra */
.algebra .topic-card:hover {
    border-color: var(--error);
}

.algebra .topic-link {
    color: var(--error);
}

.algebra .section-title::after {
    background: linear-gradient(135deg, var(--error), #dc2626);
}

/* Stats Section */
.stats-section {
    background: white;
    border-radius: var(--border-radius);
    padding: 2rem;
    margin: 3rem 0;
    box-shadow: var(--shadow);
    position: relative;
    overflow: hidden;
}

.stats-section::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--primary), var(--success), var(--warning), var(--error));
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
    text-align: center;
}

.stat-item {
    padding: 1rem;
    position: relative;
}

.stat-item::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 40px;
    height: 2px;
    background: var(--primary);
    border-radius: 1px;
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary);
    display: block;
    margin-bottom: 0.5rem;
}

.stat-label {
    color: var(--gray);
    font-size: 0.9rem;
    font-weight: 500;
}

/* Breadcrumb */
.breadcrumb-section {
    background: white;
    padding: 1rem 0;
    border-bottom: 1px solid #e2e8f0;
}

.breadcrumb {
    background: none;
    padding: 0;
    margin: 0;
    font-size: 0.9rem;
}

.breadcrumb-item + .breadcrumb-item::before {
    content: ">";
    color: var(--gray);
    margin: 0 0.5rem;
}

.breadcrumb-item a {
    color: var(--primary);
    text-decoration: none;
    transition: color 0.3s ease;
}

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

.breadcrumb-item.active {
    color: var(--gray);
}

/* Footer */
.footer {
    background: var(--dark);
    color: white;
    padding: 3rem 0 1rem;
    margin-top: 4rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

.footer-section p {
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: 1rem;
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: 0.5rem;
}

.footer-links a {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-links a:hover {
    color: white;
}

.social-links {
    display: flex;
    gap: 1rem;
    margin-top: 1rem;
}

.social-links a {
    width: 40px;
    height: 40px;
    background: var(--primary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    text-decoration: none;
    transition: background 0.3s ease;
}

.social-links a:hover {
    background: var(--primary-dark);
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: rgba(255, 255, 255, 0.6);
}

/* Navigation */
.navbar {
    background: white !important;
    box-shadow: var(--shadow);
    padding: 1rem 0;
}

.navbar-brand img {
    height: 40px;
    width: auto;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 1rem;
}

.navbar-nav .nav-link {
    color: var(--dark) !important;
    font-weight: 500;
    margin: 0 0.5rem;
    transition: color 0.3s ease;
}

.navbar-nav .nav-link:hover {
    color: var(--primary) !important;
}

.dropdown-menu {
    border: none;
    box-shadow: var(--shadow-lg);
    border-radius: var(--border-radius);
    padding: 1rem 0;
}

.dropdown-item {
    padding: 0.75rem 1.5rem;
    transition: background 0.3s ease;
}

.dropdown-item:hover {
    background: var(--gray-light);
    color: var(--primary);
}

/* Loading states */
.loading {
    opacity: 0.7;
    pointer-events: none;
}

.loading::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 20px;
    height: 20px;
    border: 2px solid transparent;
    border-top: 2px solid var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

/* Scroll to top button */
.scroll-to-top {
    position: fixed;
    bottom: 20px;
    right: 20px;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    z-index: 1000;
}

.scroll-to-top.visible {
    opacity: 1;
    visibility: visible;
}

.scroll-to-top:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }

    .profile-section {
        flex-direction: column;
        gap: 0.5rem;
        margin-top: 1rem;
    }

    .search-input {
        width: 100%;
    }

    .search-input:focus {
        width: 100%;
    }

    .hero-title {
        font-size: 2rem;
    }

    .section-title {
        font-size: 2rem;
    }

    .container {
        padding: 0 1rem;
    }

    .hero-section {
        padding: 2rem 0;
    }

    .topics-grid {
        grid-template-columns: 1fr;
    }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 576px) {
    .stats-grid {
        grid-template-columns: 1fr;
    }

    .features {
        grid-template-columns: 1fr;
    }
}

/* Animations */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes pulse {
    0%, 100% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.05);
    }
}

@keyframes spin {
    0% { transform: translate(-50%, -50%) rotate(0deg); }
    100% { transform: translate(-50%, -50%) rotate(360deg); }
}

.hero-section, .category-section {
    animation: fadeInUp 0.8s ease;
}

.feature-icon {
    animation: pulse 2s infinite;
}

.feature:hover .feature-icon {
    animation: none;
}