I'd like to tell you about a program I have on Google Play Market. https://play.google.com/store/apps/details?id=uk.co.fordartworks.SourcesGL.pro
SourcesPro is, I think, genuinely unique. It is a kind of generative graphics app, which lets you combine simple repeating "sources" and see what happens. Since a picture is worth the proverbial... http://calderwa.deviantart.com/gallery/
The app also animates these images, so you can watch the interactions change. On a decent modern device, high quality output images up to 2000 pixels per side can be created.
There is also a free version with some limitations - no fancy functions, small output only, 2 min pause after 20 mins of use. https://play.google.com/store/apps/details?id=uk.co.fordartworks.SourcesGL.lite
This is a deep program with almost infinite permutations. Maybe not for the casual user, it is probably more for the arty/creative type who likes messing about with photoshop or fractals, perhaps. It is a program to explore, to see "what if". It currently supports single level undo/redo, but multi-level is coming soon.
I hope you find this app of interest, I'm not aware of anything else just like it. This is literally my first effort at actually marketing it. Sources requires a bit of learning, but it produces images that no other graphics program on any platform, that I'm aware of, could manage without immense effort.