.gallery {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
}

.gallery-item {
    padding: 10px;
    box-sizing: border-box;
    width: 100%;
    max-width: 250px;
}

.gallery-item img {
    width: 100%;
    height: auto;
}

@media (min-width: 768px) {
    .gallery-item {
        width: calc(25.33% - 20px);
        margin: 10px;
    }
}