:root {
    --primary-color: #3776ab;
    --secondary-color: #ffd43b;
    --text-color: #333;
    --light-bg: #f8f9fa;
    --dark-bg: #343a40;
    --card-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    --hover-transition: all 0.3s ease;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--light-bg);
}

.container {
    width: 90%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 15px;
}

header {
    background-color: var(--primary-color);
    color: white;
    padding: 2rem 0;
    text-align: center;
}

header h1 {
    margin-bottom: 0.5rem;
    font-size: 2.5rem;
}

#main-nav {
    background-color: white;
    box-shadow: var(--card-shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-list {
    display: flex;
    flex-wrap: wrap;
    list-style: none;
    padding: 0;
    justify-content: center;
}

.nav-list li {
    margin: 0;
}

.nav-list a {
    display: block;
    padding: 1rem;
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    transition: var(--hover-transition);
}

.nav-list a:hover {
    color: var(--primary-color);
    background-color: rgba(55, 118, 171, 0.1);
}

main {
    padding: 2rem 0;
}

section {
    margin-bottom: 3rem;
}

section h2 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--secondary-color);
}

#intro {
    background-color: white;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: var(--card-shadow);
    margin-bottom: 2rem;
}

.category {
    padding-top: 2rem;
}

.module-cards {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
    margin-top: 1.5rem;
}

.module-card {
    background-color: white;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: var(--card-shadow);
    transition: var(--hover-transition);
}

.module-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.15);
}

.card-header {
    background-color: var(--primary-color);
    color: white;
    padding: 1rem;
}

.card-header h3 {
    margin: 0;
    display: flex;
    align-items: center;
}

.card-header h3 i {
    margin-right: 10px;
}

.card-body {
    padding: 1.5rem;
}

.module-description {
    margin-bottom: 1rem;
}

.popularity {
    display: flex;
    align-items: center;
    margin-top: 0.5rem;
    font-size: 0.9rem;
}

.stars {
    color: var(--secondary-color);
    margin-right: 0.5rem;
}

.module-link {
    display: inline-block;
    margin-top: 1rem;
    background-color: var(--primary-color);
    color: white;
    padding: 0.5rem 1rem;
    text-decoration: none;
    border-radius: 4px;
    transition: var(--hover-transition);
}

.module-link:hover {
    background-color: #2a5a8a;
}

footer {
    background-color: var(--dark-bg);
    color: white;
    text-align: center;
    padding: 1.5rem 0;
    margin-top: 2rem;
}

@media (max-width: 768px) {
    .nav-list {
        flex-direction: column;
    }
    
    .nav-list li {
        width: 100%;
        text-align: center;
    }
    
    .module-cards {
        grid-template-columns: 1fr;
    }
}