html, body {
    padding: 0;
    margin: 0;
    overflow: hidden;
}

#canvas1{
    position: absolute;
    right: 0;
    display: inline-block;
    padding: 0;
    margin: 0;
    background: aqua;
    width: 49%;
}

#canvas2{
    position: absolute;
    left: 0;
    display: inline-block;
    padding: 0;
    margin: 0;
    background: aqua;
    width: 49%;
}

#mirror {
    position: absolute;
    left: 49%;
    padding: 0;
    margin: 0;
    background: #D5D5D5;
    width: 2%;
}

#rotate {
    font-family: Arial, Helvetica, sans-serif;
    font-size: 12px;
    height: 25px;
    position: absolute;
    top: 5%;
    left: 55%;
}

#synch {
    font-family: Arial, Helvetica, sans-serif;
    font-size: 12px;
    height: 25px;
    position: absolute;
    top: 7%;
    left: 55%;
}

.sel{
    width: 15%; 
    position: absolute; 
    left: 5%; 
    font-size: 16px;
    font-family: 'Lucida Sans', 'Lucida Sans Regular', 'Lucida Grande', 'Lucida Sans Unicode', Geneva, Verdana, sans-serif;
    border: 1px black;
    height: 2%;
    margin: 0;
    background-color: cornflowerblue;
    color: antiquewhite;
    cursor:  pointer;
}
.sel:hover{
    background-color: limegreen;
}

.undo{
    width: 15%; 
    position: absolute; 
    left: 5%; 
    font-size: 16px;
    font-family: 'Lucida Sans', 'Lucida Sans Regular', 'Lucida Grande', 'Lucida Sans Unicode', Geneva, Verdana, sans-serif;
    border: 1px black;
    height: 2%;
    margin: 0;
    background-color: cornflowerblue;
    color: antiquewhite;
    cursor:  pointer;
}
.undo:hover{
    background-color: limegreen;
}