*{margin:0;padding:0}
html,body,div{height:100%}
div{background:#ccc;width:200px;position: relative;transition: .3s;-moz-transition: .3s;-webkit-transition: .3s;-o-transition: .3s;}
div em{position: absolute;width:6px;height:40px;background:#999;top:50%;right:-6px;margin-top:-20px;border-radius:0 5px 5px 0;cursor: pointer;}
div.on{margin-left:-200px}
div.on em:after{content:'';position: absolute;width: 0;height: 0;border-top: 4px solid transparent;border-right: 3px solid #fff;border-bottom: 4px solid transparent;border-left: 0 solid transparent;right: 2px;top:50%;margin-top:-4px}