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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.container-fluid {
    display: flex;
    min-height: 100vh;
}

/* Sidebar Styles */
.sidebar {
    width: 250px;
    background-color: white;
    border-right: 1px solid #e0e0e0;
    padding: 20px;
    position: fixed;
    height: 100vh;
    overflow-y: auto;
}

.logo {
    display: flex;
    align-items: center;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 1px solid #e0e0e0;
}

.logo svg {
    margin-right: 10px;
}

.logo span {
    font-size: 1.2rem;
    font-weight: bold;
    color: #4682B4;
}

nav ul {
    list-style: none;
}

.nav-item {
    display: flex;
    align-items: center;
    padding: 12px 16px;
    margin-bottom: 8px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
    color: #666;
}

.nav-item a {
    display: flex;
    align-items: center;
    color: inherit;
    text-decoration: none;
    width: 100%;
}

.nav-item:hover {
    background-color: #f0f8ff;
    color: #4682B4;
}

.nav-item.active {
    background-color: #e3f2fd;
    color: #4682B4;
    font-weight: bold;
}

.nav-item svg {
    margin-right: 10px;
}

.nav-section {
    margin-top: 30px;
    padding-top: 20px;
    border-top: 1px solid #e0e0e0;
}

.nav-section h3 {
    font-size: 0.9rem;
    color: #999;
    margin-bottom: 10px;
    padding: 0 16px;
}

/* Main Content Styles */
.main-content {
    flex: 1;
    margin-left: 250px;
    min-height: 100vh;
}

/* Banner Styles */
.banner {
    background: linear-gradient(135deg, #87CEEB 0%, #4682B4 100%);
    color: white;
    padding: 60px 40px;
    margin-bottom: 40px;
}

.banner-content {
    max-width: 1000px;
    margin: 0 auto;
}

.banner h1 {
    font-size: 2.5rem;
    margin-bottom: 20px;
    font-weight: 700;
}

.banner p {
    font-size: 1.1rem;
    margin-bottom: 10px;
    opacity: 0.9;
}

/* Subject Cards Styles */
.subject-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    padding: 0 40px;
    margin-bottom: 60px;
}

.subject-card {
    background: white;
    border-radius: 10px;
    padding: 30px;
    text-align: center;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease;
}

.subject-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
}

.subject-icon {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 20px;
}

.subject-icon.physics {
    background: linear-gradient(135deg, #9c27b0 0%, #673ab7 100%);
}

.subject-icon.chemistry {
    background: linear-gradient(135deg, #e91e63 0%, #c2185b 100%);
}

.subject-icon.biology {
    background: linear-gradient(135deg, #4caf50 0%, #388e3c 100%);
}

.subject-icon.math {
    background: linear-gradient(135deg, #ff9800 0%, #f57c00 100%);
}

.subject-card h3 {
    font-size: 1.2rem;
    margin-bottom: 10px;
    color: #333;
    font-weight: 600;
}

.subject-card p {
    color: #666;
    font-size: 0.9rem;
}

/* Featured Experiments Styles */
.featured-experiments {
    padding: 0 40px;
    margin-bottom: 60px;
}

.featured-experiments h2 {
    font-size: 1.8rem;
    margin-bottom: 30px;
    color: #4682B4;
    font-weight: 700;
}

.experiment-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
}

.experiment-card {
    background: white;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.experiment-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
}

.experiment-image {
    position: relative;
    height: 200px;
    overflow: hidden;
}

.experiment-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.3s ease;
}

.experiment-card:hover .experiment-image img {
    transform: scale(1.05);
}

.experiment-level {
    position: absolute;
    top: 10px;
    right: 10px;
    background: rgba(0, 0, 0, 0.7);
    color: white;
    padding: 5px 10px;
    border-radius: 4px;
    font-size: 0.8rem;
}

.experiment-card h3 {
    font-size: 1.2rem;
    margin: 20px 20px 10px;
    color: #333;
    font-weight: 600;
}

.experiment-card p {
    margin: 0 20px 20px;
    color: #666;
    font-size: 0.9rem;
    line-height: 1.5;
}

.btn {
    display: inline-block;
    background: linear-gradient(135deg, #87CEEB 0%, #4682B4 100%);
    color: white;
    padding: 12px 24px;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s ease;
    font-size: 14px;
    box-shadow: 0 4px 12px rgba(70, 130, 180, 0.3);
    margin: 0 20px 20px;
}

.btn:hover {
    background: linear-gradient(135deg, #7EC0EE 0%, #3A6EA5 100%);
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(70, 130, 180, 0.4);
}

/* Footer Styles */
footer {
    background: #4682B4;
    color: white;
    text-align: center;
    padding: 30px 0;
    margin-top: 60px;
    margin-left: 250px;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container-fluid {
        flex-direction: column;
    }
    
    .sidebar {
        width: 100%;
        height: auto;
        position: relative;
        border-right: none;
        border-bottom: 1px solid #e0e0e0;
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .banner {
        padding: 40px 20px;
    }
    
    .banner h1 {
        font-size: 2rem;
    }
    
    .subject-cards {
        padding: 0 20px;
        grid-template-columns: repeat(2, 1fr);
    }
    
    .featured-experiments {
        padding: 0 20px;
    }
    
    .experiment-grid {
        grid-template-columns: 1fr;
    }
    
    footer {
        margin-left: 0;
    }
}

@media (max-width: 480px) {
    .subject-cards {
        grid-template-columns: 1fr;
    }
    
    .banner h1 {
        font-size: 1.5rem;
    }
}