BrowserQuest a massively multiplayer HTML5 game experiment
hacks.mozilla.org/2012/03/browserquest
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
BrowserQuest is a tribute to classic video-games with a multiplayer twist. You play as a young warrior driven by the thrill of adventure. No princess to save here, just a dangerous world filled with treasures to discover. And its all done in glorious HTML5 and JavaScript.