See demo on Codepen: https://codepen.io/comehope/pen/odpRKX
Watch interactive screencast on Scrimba: https://scrimba.com/c/cmQV7Hd
Read annotated source on Segmentfault(zh-cn): https://segmentfault.com/a/1190000014785816
Inspired by: Mike Schultz https://codepen.io/mike-schultz/pen/NgQvGO