See demo on Codepen: https://codepen.io/comehope/pen/JvmBdE
Watch interactive screencast on Scrimba: https://scrimba.com/p/pEgDAM/cp2edUD
Read annotated source on Segmentfault(zh-cn): https://segmentfault.com/a/1190000014895634
Inspired by: Rico Sta. Cruz https://codepen.io/rstacruz/pen/oxJqNv