.hero-section {
    background: linear-gradient(rgba(0, 0, 0, 0.7), rgba(0, 0, 0, 0.7)), url('img/fisica-background.jpg');
    background-size: cover;
    background-position: center;
}
.feature-icon {
    width: 4rem;
    height: 4rem;
    font-size: 2rem;
}
.topic-card {
    transition: transform 0.3s ease;
    height: 100%;
}
.topic-card:hover {
    transform: translateY(-5px);
}