I'm trying to run an animation by altering the `background-position` of an image within a `div`. I'm using `setTimeout` to recall the function and continuously decrement the image position (so it appears to be animated). I've tested the the variables and `setTimeout` they seem to be working fine. The image however is not moving at all. 

How can i amend the code to enable this animation to run ?

```
var decrement = 0;

function runningRobot() {
var robotCont = document.getElementById('robotCont');

  if(decrement < -660) {
  decrement = 0;
}
 robotCont.style.backgroundPositon = decrement+ 'px' +' '+ 0 + 'px';
decrement -= 110;  
timer = setTimeout(runningRobot,500);
}

runningRobot();

```