This is not really a game, but a tool to create artwork/graphics. It's very easy to use, all you need to do is continuously select the best or most interesting image you see on the screen.
What you see are randomly mutating images, generated from a code (which is displayed at the bottom). When you click on one of the 16 images, you get the full-size version at the right and all images start mutating from that point, so you get lots of mutations of your selected image. If none of those turn out to be any good, you can click on the large image, which will restart the current code. You can go back to a previously selected image by pressing BACKSPACE.
Sometimes an image will change just before you click on it and you get an unwanted mutation. In that case, press SHIFT+BACKSPACE.
Other keys you can use are:
M: fast mutation
S: change size (256x256 / 512x512)
T: transparency on / off
R: reset all
+ / -: change length of code
CTRL+C / CTRL+V: copy / paste code
Once you have found an image you want to use for something else, you could capture the screen and save it as a bitmap, but the idea is to save the code (which is of course a lot smaller) and generate the image when you need it. At the moment the code to generate images is only available in haXe: ArtGen.hx (but it shouldn't be too hard to port this to as3).
Here are a few examples of codes you can try (copy and paste them into the program):
(only the code, no text!)
f7ce96550e1669f7a4 (chess board)
119300acacaacb4449421f2ed 64d1e (grass)
fc766e1e81fb265b678a7f93c 32fcfe145 (checkmark)
2dab323c3cc31ed5ff8940f05 eac735ccc5e (planet)
f16628a95bc6cbfabb421f99d 609874ddb37478d9f1eaf7f07 96c3663b1f504e0550 (sky)
590a737e502df0b7babe2fa1b eaca25614ba1e9724e7 (tiles)
240a1d7e50dcf0b7c19a29a1c eaca25678ba94f6241ef15b (wall)
Enjoy, and if you find a really nice code, post it in the comments!