I know nothing about actual genetic algorithms, but I did try to create my own artificial "genes."
Basically, each Pixel has ten values stored for each attribute (size, color, and shape). When you breed Pixels, the children randomly select nine values, and then add one value that's the average of the other values.
Then, one of those values is randomly selected to be the actual attribute that you see.
Of course, there's a bit more going on (mostly to keep it somewhat more consistent) but that's at the core of it.
Thanks for playing! Glad you enjoyed it, and sorry to hear you had some control issues, I've found using a mouse to be slightly more reliable than touchscreen, but it's going to depend on screen size, etc. and I didn't have time to test it on anything other than my phone and computer.