Simple Animation test

I've made a small animation test, trying to mimic this simple effect My code is available here and this is a screen-capture recording the results. 4 browsers from left to right: IE11 - a complete mess, not web worthy... then Microsoft Edge 13 - notice a round circle is a bit too much to ask... I used border-radius. Then comes the mighty Google chrome - notice how the animation elements are pixelated during the animation to achieve "performance"... and last is Firefox which is the only browser that delivered a sharp result although the movement was a bit jumpy lacking smoothness and elegance. I've used GSAP which uses a css plugin to animate the css properties via JS. Someone please tell me how this site is looking great even on IE11? It uses the same GSAP animation library as mentioned here... Any thoughts on techniques they may have used to improve the appearance of these animation?