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

body {
    font-family: Arial, sans-serif;
}

header {
    background-color: #333;
    color: white;
    text-align: center;
    padding: 20px;
}

footer {
    background-color: #333;
    color: white;
    text-align: center;
    padding: 10px;
    position: fixed;
    bottom: 0;
    width: 100%;
}

main {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 20px;
    padding: 20px;
}

.box {
    position: relative;
    width: 200px;
    height: 200px;
    border: 1px solid #ccc;
    overflow: hidden;
}

.box img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: opacity 0.3s ease;
}

.hover-img {
    opacity: 0;
    position: absolute;
    top: 0;
    left: 0;
}

.box:hover .hover-img {
    opacity: 1;
}

.box:hover .default-img {
    opacity: 0;
}