gistfile1.js

;( function( $ ) {
	var 	$background,
		mouse = {
			x: 0, // Current x-axis position of mouse
			y: 0, // Current y-axis position of mouse
			lx: -1, // Last iteration x-axis position of mouse
			ly: -1, // Last iteration y-axis position of mouse
		};

	$( document ).on( 'mousemove', function( event ) {
		mouse.x = event.clientX || event.pageX;
		mouse.y = event.clientY || event.pageY;
	} );

	var mouse_loop = function() {
		// Avoid calculations if not needed
		if ( mouse.x == mouse.lx && mouse.y == mouse.ly ) {
			rAF( mouse_loop );
			return false;
		}
		else {
			mouse.lx = mouse.x;
			mouse.ly = mouse.y;
		}

		$background.css( {
			'transform': 'translate( ' + ( ( $( window ).width() / 2 - mouse.lx ) / $( window ).width() * 100 ) + 'px, ' + ( ( $( window ).height() / 2 - mouse.ly ) / $( window ).height() * 100 ) + 'px )'
		} );

		rAF( mouse_loop );
	};

	$( document ).on( 'ready', function() {
		$background = $( '.background-wrapper' );

		mouse_loop();
	} );
} ) ( jQuery )