There is another way of doing this with just JavaScript. All you have to do is toggle the visibility based on the current state of the DIV's visibility in CSS.
Example:
function toggleVideo() {
var e = document.getElementById('video-over');
if(e.style.visibility == 'visible') {
e.style.visibility = 'hidden';
} else if(e.style.visibility == 'hidden') {
e.style.visibility = 'visible';
}
}