* {
    margin: 0;
    padding: 0;
}
.product {
    margin-left: 50px;
    width: 500px;
}

.product-img {
    margin: 20px auto;
    text-align: center;
}

.showimg {
    position: relative;
    width: 500px;
    height: 375px;
    border: 1px solid #f5f5f5;
}

.show {
    width: 500px;
    height: 375px;
}

.product-img img {
    margin: 0 3px;
    width: 80px;
    height: 60px;
    border: 2px solid #FFF;
}

.showbox {
    position: absolute;
    top: 0;
    left: 0;
    opacity: 0.5;
    cursor: move;
    width: 200px;
    height: 200px;
    background-color: lightblue;
    display: none;
}

.showlarge {
    position: absolute;
    overflow: hidden;
    top: 0;
    left: 520px;
    width: 500px;
    height: 375px;
    border: 1px solid #f5f5f5;
    z-index: 99;
    display: none;
}

.showlarge img {
    width: 960px;
    height: 720px;
    position: absolute;
}
@media (max-width:720px) {
    .product{width: 100%;margin-left: 0;}
    .showimg{width: 100%;height: auto;}
    .show{width: 100%;height: auto;}
}