.gallery {
    box-sizing: border-box;
    display: flex;
    flex-wrap: wrap;
    margin: 10px auto;
    max-width: 850px;
    position: relative;
    padding-top: 560px;
}

.gallery img {
    max-width: 100%;
    max-height: 560px;
    vertical-align: top;
}

.gallery > div > img {
    position: absolute;
    top: 0;
    left: 0;
    opacity: 0;
    transition: opacity 0.3s ease-in-out;
}

.gallery > div > label {
    padding-top: 6px;
    margin: 6px;
    display: block;
}

.gallery > div > input {
    position: absolute;
    opacity: 0;
    visibility: hidden;
}

.gallery > div > label > img {
    max-width: 150px;
}

.gallery > div > input:checked + img {
    opacity: 1;
}

.gallery > div > input:checked ~ label > img {
    box-shadow: 0 0 0 3px #333;
}