.overlay {
    position: fixed;
    display: none;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0,0,0,0.5);
    z-index: 2;
    cursor: pointer;
}

.overlaybutton {

}

#drop_zone {
  border: 5px solid blue;
  width:  200px;
  height: 100px;
}