function changeImageOn(anImage) {
   document.images[anImage].src = document.images[anImage].src.replace("_off", "_on");
}

function changeImageOff(anImage) {
   document.images[anImage].src = document.images[anImage].src.replace("_on", "_off");
}

function changeImage(anImage, anFile) {
   document.images[anImage].src = anFile;
}

function done() {
  loaded = true;
}