I did that as well! Beautiful stuff, good on the developer.

So, the technical part isn’t that crazy tbh — as soon as you respect some pretty straightforward principles you should be fine (animate only transform/opacity, favour requestAnimationFrame over setInterval, transitionend/animationend events over setTimeout, …). The complicated part was mostly the “creative” process, ie. how fast should the animation run (some people read, others don’t), what's the appropriate bezier-curve, how make the play button “engaging” enough so people don’t feel like they’re gonna watch a billion-hour screencast, etc.