Zoom on mouse position

zoom.js

var toggle = true;

function mouseFlicker(e) {

	if(toggle) {

		var multiplier = Math.round(Math.random()*1)+3;
		var width = window.innerHeight*wish.imageRatio;
		var height = window.innerHeight;
		var newWidth = width*multiplier;
		var newHeight = height*multiplier;
		var mouseX = e.pageX*multiplier;
		var mouseY = e.pageY*multiplier;
		var halfWidth = window.innerWidth/2;
		var halfHeight = window.innerHeight/2;
		var top = mouseY-halfHeight;
		if(top < 0) top = 0;
		var left = mouseX-halfWidth;
		if(left < 0) left = 0;

		if((newHeight-top) < window.innerHeight) {
			top = newHeight - window.innerHeight;
		}
		if((newWidth-left) < window.innerWidth) {
			left = newWidth - window.innerWidth;
		}

		$('#wishes').css({
			'background-size' : newWidth+'px '+newHeight+'px',
			'background-position' : '-'+left+'px -'+top+'px '
		});
		toggle = false;
	} else {

		$('#wishes').css({
			'background-size' : 'cover',
			'background-position' : 'top left'
		});
        
		toggle = true;
	}
}