Download source of Bacteria 2
This game is creaed with Game Maker 7 pro from YoYo Games. A registered version is required to run the source code.
Also, this source is available for educational purposes. Look through it and see if you can learn something from this source code. Your free to take some inspiration from the source for your own game but don't try to make a Bacteria 3. There are plenty of open source games on my Game Maker website to help you get started with a simple engine.
There is also some documentation available on how the Arteficial Intelligence works.