Richard Dawkins's 1986 biomorphs let you breed drawings by choosing favourites. Do the same here: the middle picture is the parent, the eight around it are mutants; click the one you like and it becomes the parent. You are the fitness function. Everything runs in your browser; nothing leaves it.
Click or press Enter/Space on a tile to make it the new parent; its eight neighbours are then redrawn as fresh mutants of it. Raise the mutation rate for changes that touch more of the genome at once, and the mutation strength for wilder individual changes. Undo steps back one generation; Reset draws a brand new parent from the seed above.