Gene is a genetic algorithm in 60 lines of (non-PEP8) Python 2.6+ code, with minimal imports.
60 lines of python should fit on ONE SCREEN!

This algorithm is *NOT* just making random guesses. It starts randomly, and there is randomness in it, but the principle is much more complex. See http://en.wikipedia.org/wiki/Genetic_algorithm#The_building_block_hypothesis

To play, you will need to:
1. Install Python. See python.org
2. Clone the source code with git or save this somewhere: https://github.com/mpath/gene/blob/master/gene.py
3. Run gene at a command prompt, like so: python path/to/gene/gene.py

4. You will be prompted for a string to "strive towards". You may use upper and lowercase letters and spaces, but not punctuation or numbers. Type it out (it can be as long as you'd like) and hit ENTER.
5. The genetic algorithm will run and update after every generation. At the end you will see some stats. Enjoy the show!

HINT: If it's taking too long to complete generations, try a shorter string.