.wrapper {
    position: relative;
}

.image-box {
    position: absolute;
    top: 50%;
    left: 50%;

    transform: translate(-50%);
}

.viewer-box {
    position: relative;
}

.viewer-box #image-viewer {
    user-select: none;
}

.viewer-box #bi-clo {
    display: inline-block;

    width: 84px;
    height: 30px;

    background-size: 100% 100%;
    position: absolute;
    right: 10px;
    bottom: 10px;
}

.btn-prev {
    float: left;
}
.btn-next {
    float: right;
}