if (document.images) {
  var alienoff = new Image(); alienoff.src = "aliens/alien1.jpg";
  var aliencenter = new Image(); aliencenter.src = "aliens/alien10.jpg";
  var alienleft = new Image(); alienleft.src ="aliens/alien6.jpg";  
  var alienright = new Image(); alienright.src ="aliens/alien2.jpg";
  var alienup = new Image(); alienup.src ="aliens/alien4.jpg";
  var aliendown = new Image(); aliendown.src ="aliens/alien8.jpg";
  var alienupright = new Image(); alienupright.src ="aliens/alien3.jpg";
  var aliendownright = new Image(); aliendownright.src ="aliens/alien9.jpg";
  var alienupleft = new Image(); alienupleft.src ="aliens/alien5.jpg";
  var aliendownleft = new Image(); aliendownleft.src ="aliens/alien7.jpg";
}

function danceOn(imgName) {
  if (document.images) 
    document[imgName].src = eval(imgName + 'on.src');
}

function danceOff(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'off.src');
}

function danceLeft(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'left.src');
}

function danceRight(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'right.src');
}

function danceUp(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'up.src');
}

function danceDown(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'down.src');
}

function danceUpLeft(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'upleft.src');
}

function danceUpRight(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'upright.src');
}

function danceDownLeft(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'downleft.src');
}

function danceDownRight(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'downright.src');
}

function danceDownRight(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'downright.src');
}

function danceCenter(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + 'center.src');
}