.thumbnail {
    width: 60px;
}

.thumbnail:hover {
    border-bottom: 2px solid red;
    margin-bottom: -2px;
}

#mainImage {
    height: 300px;
    width: 300px;
    margin-bottom: 10px;
    transition: opacity 0.5s;
    position: relative;
}

.invisible {
    opacity: 0;
}

#mainImage img {
    opacity: 0;
    position: absolute;
}

.visible {
    opacity: 1 !important;
}

.current {
    border-bottom: 2px solid red;
    margin-bottom: -2px;
}