ate of touch relative to the viewport (excludes scroll offset)
 *	screenX: Relative to the screen
 *	screenY: Relative to the screen
 *	pageX: Relative to the full page (includes scrolling)
 *	pageY: Relative to the full page (includes scrolling)
 */	

function onTouchStart(e) {
 
	for(var i = 0; i<e.changedTouches.length; i++){
		var touch = e.changedTouches[i]; 
		//console.log(leftTouchID + " " 
		
		if(touch.clientX <= halfWidth){			
			leftTouchID = touch.identifier; 
			leftTouchStartPos.reset(touch.c