body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    margin: 0;
    padding: 0;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 40px 20px;
}

header {
    text-align: center;
    margin-bottom: 50px;
    color: white;
}

header h1 {
    font-size: 3rem;
    margin: 0 0 10px 0;
    font-weight: 700;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.2);
}

.subtitle {
    font-size: 1.2rem;
    opacity: 0.9;
    margin: 0;
}

.loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 300px;
    color: white;
}

.spinner {
    border: 4px solid rgba(255, 255, 255, 0.3);
    border-top: 4px solid white;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    animation: spin 1s linear infinite;
    margin-bottom: 20px;
}

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

.error {
    text-align: center;
    color: white;
    padding: 40px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 10px;
    backdrop-filter: blur(10px);
}

.error button {
    margin-top: 20px;
    padding: 12px 30px;
    background: white;
    color: #667eea;
    border: none;
    border-radius: 5px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.error button:hover {
    background: #f0f0f0;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 25px;
    margin-top: 20px;
}

.course-card {
    background: white;
    border-radius: 15px;
    padding: 30px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.2);
}

.course-icon {
    font-size: 4rem;
    margin-bottom: 15px;
}

.course-name {
    font-size: 1.5rem;
    font-weight: 600;
    color: #333;
    margin: 0 0 10px 0;
    word-wrap: break-word;
}

.course-id {
    font-size: 0.9rem;
    color: #666;
    margin: 0 0 10px 0;
}

.course-secondary {
    font-size: 1rem;
    color: #555;
    margin: 0 0 10px 0;
    font-style: italic;
}

.course-instructor {
    font-size: 0.9rem;
    color: #444;
    margin: 0 0 20px 0;
    font-weight: 500;
}

.start-chat-btn {
    padding: 12px 30px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    border-radius: 25px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 2px 8px rgba(102, 126, 234, 0.4);
}

.start-chat-btn:hover {
    transform: scale(1.05);
    box-shadow: 0 4px 12px rgba(102, 126, 234, 0.6);
}

.hidden {
    display: none !important;
}

/* Responsive design */
@media (max-width: 768px) {
    header h1 {
        font-size: 2rem;
    }
    
    .subtitle {
        font-size: 1rem;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
    }
    
    .container {
        padding: 20px 15px;
    }
}