See demo on Codepen: https://codepen.io/comehope/pen/jKVbyE
Watch interractive video on Scrimba: https://scrimba.com/p/pEgDAM/cD8nMUr
Read annotated source on Segmentfault(zh-cn): https://segmentfault.com/a/1190000015221260
Inspired by: J Howell https://codepen.io/lixquid/pen/mBnyu