.mousedir {
  position: relative;
  -webkit-box-sizing: border-box;
     -moz-box-sizing: border-box;
          box-sizing: border-box;
  width: 100%;
  height: 100%;
  overflow: hidden;
  border: 1px solid rgba(0, 0, 0, 0.1);
}

.mousedir dt {
  width: 100%;
  height: 100%;
}

.mousedir dd {
  position: absolute;
  top: 100%;
  bottom: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 255, 0.5);
}