The Sparkle series of games use a 2D layout and a "zen" approach, putting players in the role of a tiny plankton-like creature as it eats, grows, and evolves. The third game steps up the design of both the sea life and the background until it looks like you're playing in a catastrophic oil spill comprised entirely of tie-dye. Eat, grow, and try not to be eaten in return as you swim through the levels.
There's a dedicated "amoeba" sub-genre out there (it works pretty well on touchscreens) but Sparkle 3 Genesis adds some much-needed complexity. Different food sources will make your creature grow in different ways, introducing a crafting element, and twelve different levels and intermittent screen-filling bosses lend structure to an other wise nebulous experience. Specific objectives and quests require you to learn the mechanics of the microscopic world.
Sparkle 3 Genesis costs $3 and has no ads or in-app purchases - that's what we like to see. It's compatible with Android 4.0.3 and higher, and technically with Android TV as well, but like some other recent games, this appears to be unintentional. It's miscategorized on the SHIELD TV home screen and won't respond to controller inputs.