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

.image-box {
    transition: opacity 0.3s ease;
}

.image-box:hover ~ .image-box {
    opacity: 0.5;
}

.row:hover .image-box {
    opacity: 0.5;
}

.row:hover .image-box:hover {
    opacity: 1;
}