The game engine is programmed in C++, all the .net languages are way to slow. Here you can download the sourcode of quake: Here is the deal. No one is going to write an entire game of any sophistication in Java or .Net. As mentioned, there are much faster solutions. But the good news is that it doesn't matter - in most cases the really speed critical stuff (ie; handling graphics, audio, etc) is already done for you and available in a number of libraries, whether ultimately coded in C++, C, Assembler, or a combination thereof. Writing Java/.Net games that utilize these is therefore a perfectly reasonable proposition, and unless you're doing some heavy AI work, you're going to be plenty fast enough. Sit down with something like the SDL and/or OpenGL libraries and you'll find that you can create some very fast and beautiful games indeed. And to completely befuddle many of the '.Net aint fast enough' experts here, write it in VB.Net or IronPython or somesuch. I guarantee that for any games a single developer/small shop can come up with, if you are able to exploit common libraries to do all of your heavy lifting, you are going to be: 1) Plenty performant enough (machine cycles). 2) Be able to outpace your counterparts who've been brainwashed into thinking they have to create games completely in C/C++ (developer cycles). Best regards as always, Steve