[Edit] (The quit feature I added isn’t working as planned. If you download the build file from github and open index.html the code works. However, both gamebucket.io and sharemygame.io do not allow the url to change. Back to square one.)
So here’s my version of Number Wizard.
However, I figured out a clever way to quit. I used Application.OpenURL (); and put the url to this page, so when you quit it directs you back to my post. Not bad 
Cheers!
This is probably because your game is actually being loaded inside an iFrame on that page. Chances are without using one of those services, it would be fine, e.g. if you have your own hosting space. 
A useful feature of your approach would be that you could potentially redirect the user to a web page which says “Did you enjoy the game? How would you rate it?” and then give them some stars to click on for general feedback, or perhaps a text area to add additional comments. Only useful really for the web-based game(s) though.
Thanks for the input. And I agree, directing to a page for feedback would be awesome!
I played your game, and it is pretty good. But the fact that you figured out how to quit out of a WebGL build is super impressive. That is really clever. Fantastic job. Thanks for giving me ideas for my game. That has to be the coolest feature I have yet seen in a game (and I’ve played a bunch of them). When I did searches for quit Web GL they all told me it was impossible.