.thumbnail-wall {
    column-width: 250px;
    column-gap: 0;
}
.thumbnail-wall img {
    width: 100%;
    display: block;
    margin-bottom: 0;
}
.art-modal {
    display: none;
    position: fixed;
    z-index: 999;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0,0,0,0.95);
}
.art-modal-content {
    display: block;
    margin: 60px auto 20px auto;
    max-width: 90%;
    max-height: 80vh;
    box-shadow: 0 0 30px rgba(255,255,255,0.2);
}
.art-caption {
    text-align: center;
    color: #ccc;
    font-family: monospace;
    font-size: 14px;
    padding: 10px;
    width: 90%;
    margin: auto;
}
.art-close {
    position: absolute;
    top: 20px;
    right: 30px;
    font-size: 32px;
    color: #999;
    cursor: pointer;
    font-family: monospace;
}
.art-close:hover {
    color: #fff;
}