html,
body
{
    height: 100%;
    padding: 0px;
    margin: 0px;
}

#gallery
{
    width: 100%;
}

#viewer
{
    height: calc(100vh - 167px);
    width: 100%;
}

.draggable
{
    width: 90%;
    margin: 0 auto;
    padding: 5px 20px;
    border: 1px dotted black
}