I worked at a startup that had an unusually fancy landing page. I noticed that it was sluggish on my laptop. Someone pointed out there phone tended to heat up when showing it off to customers. We poked into what the contractor had done. They apparently used some bezier curves to animate stuff in a nice way. Each time the animation moved it computed the entire bezier curve to some superfine detail then picked a point in it and put the elements on the page.