How to make a moving uploader of the minimum size and beautiful

I want to share a little trick to create an animated download bar as in flash players or in the operating system.
We have in stock just a picture:


How to make it move? And very easy! It is necessary to move the background in the interval pixel by pixel.
Watch the demo


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If you have not looked at the source text of the page I will give here the code:
var xPos=0;
function move_bg(){
$("#load_td").css( {backgroundPosition: xPos+'px 0px'} );
if(xPos == 60){
xPos=0;
}
xPos++;
}


The function in the interval, each call increases by 1 the value by which the pixel needs to be shifted, when the value reaches the width of the background image, it is reset to 0 so an imperceptible change occurs.

Probably the method has long been used, but I came to it myself, I hope someone will come in handy.