keypress

https://stackoverflow.com/questions/5203407/how-to-detect-if-multiple-keys-are-pressed-at-once-using-javascript

https://stackoverflow.com/questions/3902635/how-does-one-capture-a-macs-command-key-via-javascript

https://github.com/tzuryby/jquery.hotkeys

Example

http://shauninman.com/playdate/ratcheteer/