One thing you may hear about from time to time in the games industry is an event called a "game jam." What a game jam is is nothing more than a few game developers getting together for a weekend and knocking a game out. The game may not have very high production values or a lot of gameplay or even work, but the whole point is to experiment with different gameplay. Most of the time, the results of these jams aren't seen by the public, but on occasion one will seep out.
This is from a game jam I participated in back 0n February 20 and 21 2005, with some minor modifications through to February 24, 2005. It will not work as is. It uses Managed DirectX and Visual Basic .NET 2003 and is distributed in source form. Once you are able to get it to run, you'll find the assets for four levels but only the level data for one. I'm not all that happy with my coding style at the time, but I'm happy to say that the quality of my code has improved dramatically since then.
I've also included the source code for SplitTGA, the tool used to split the original 4096x4096 TGA files into the smaller TGA tiles. To be honest, I should have converted them to JPG files.
Download "Infection: Viral Defense 3D" (297Mb)
This download may go away soon depending on the traffic load on my webhost, but given that I just renewed for a year, it should be up for a little bit.