.wallpaper {
    position: fixed;
    top: 0;
    left: 0;
    z-index: -1;
    width: 100%;
    height: 100vh;
    opacity: 0.05;
    background-image: url('../images/wallpaper.jpg');
    background-repeat: no-repeat;
    background-size: cover;
    animation: zoom-in-out 10s infinite alternate;
}

@keyframes zoom-in-out {
    0% { transform: scale(1); }
    50% { transform: scale(1.4); }
    100% { transform: scale(1); }
}