Jerome Renaux has taken the original Mozilla game, BrowserQuest, and converted it to run under Phaser. It uses the originals graphics and map layout, but is an all new implementation under the hood, and thankfully just as fun as the original :)
Explore the world, find better equipment, fight monsters and defeat the final boss - alone or with friends.
There is in-game chat, achievements, NPCs to talk to, chests to find, weapons to equip and generally lots of fun to be had. I did manage to level my way up, and defeated the Skeleton King (with a pale blue sword and red armor) but alas there was no great fanfare at the end!
Mind you, the game is open source and released under the MIT license - so feel free to add that in yourself :)