The aim of this document is to get you started with developing applications for Node.js, teaching you everything you need to know about "advanced" JavaScript along the way. It goes way beyond your typical "Hello World" tutorial. You are reading the final version of this book, i.e., updates are only done to correct errors or to reflect changes in new versions of Node.js.
Its 2D tile graphics engine is powered by HTML5 Canvas, with browser-to-server communications handled by WebSockets. Sound effects, meanwhile, are powered by HTML5 audio APIs, and each player's progress is saved using localStorage. The game also supports lots of simultaneous players, thanks to a JavaScript-coded backend that runs on Node.js.