Zen Koi is a very special game where you control the motion of a small fish that swims through a pond trying to eat plankton and smaller fish so it can level up and try to find another fish to mate with.
Gameplay is quite simple. Tap the screen anywhere to move your fish in that direction. If you tap on a plankton you'll chase it down till you eat it, though starting out your fish is very, very slow. As you level up, though, you can improve certain attributes.
The pond your fish swims in is full of surprises. Sometimes you can collect power-ups to move faster, but there are also activators that let you increase the size of the pond. Towards the end, other fish will occasionally appear and you can try to mate with them.
Zen Koi is a highly interesting experience that is especially enjoyable with headphones, as the game is a proper audiovisual delight. This on top of the fact that the game system is original and quite entertaining.