Catch-22 ($0.99) by Mango Down! is a one tap puzzle game that's simple to play but tough to master. This is a game that doesn't come with instructions, but luckily, it's easy enough to figure out.
There are two orbs in blue and green that orbit a glowing, dreamlike orange planet. You control one orb at a time, and tap to jump up in the air when the two orbs approach one another (they circle in opposite directions). The goal is to avoid collisions.
One orb at a time is the main orb, and the other is the ghost orb. As you play, you will collect smaller orbs that increase your score, and once you collect all of the tiny orbs on a single revolution, the larger orbs will switch position, going in the opposite direction.
The ghost orb becomes the main orb and the previous orb then becomes the ghost orb, and the key to getting a high score is to master the switching and keep the orbs from running into another with well timed jumps.
Your current ghost orb will follow the path that you made when it was the main orb, so it's also important to remember your previous path, which will keep you alive. You're essentially playing against yourself every round, avoiding your past jumps with all new jumps.
If this sounds confusing, it is. Honestly, this game could do with a short tutorial or introduction to teach players how to maneuver, but once you get the hang of it, its simplicity is surprisingly addictive.
Thanks to the repetitive gameplay and the soothing colors, Catch-22 is one of those inherently relaxing games like Osmos or Eufloria. Still, this is not a game that is for everyone. It's ultra simple with only one game mode, though there are leaderboards and achievements that add some depth.
While I do recommend this game, I'd suggest trying it out before you buy. You can give it a whirl on the Catch-22 Facebook page.