I've wanted to build such a game for ages and have done (not very well) in the past (
http://www.youtube.com/watch?v=lpM-wKLTKSI), this version is designed to run in single player, but also to be able to connect to a Node server to enable multiplayer (currently only map/chat works, but PvP is the idea). The multiplayer is half-implemented currently, if you select 'connect to server' on the bottom right menu and use host pkrusset.com with port 9030 it should connect up (return to chat).
Github: https://github.com/Fizzadar/PK-Russet