Anyone interested in learning how to code such games can have a look at my open source Terrarium.js http://terrariumjs.wiselabs.net http://terrariumjs.wiselabs.

Anyone interested in learning how to code such games can have a look at my open source Terrarium.js http://terrariumjs.wiselabs.net http://terrariumjs.wiselabs.net (it has a multiplayer component)