Semispheres

It's pretty good, worth the priceDeserves more love from fans of abstract puzzley/stealth stuff.
**I don't think it would be any fun without a proper controller (with 2 joysticks).
Each level is split vertically into 2 halves, as you can see from the store screenshots. You control 2 spheres (jellyfish?) simultaneously, and need to get each to the exit on their side of the board. For most levels, you can usually split up the task to work on one side at a time, alternating back and forth, but there are definitely levels that require active, simultaneous control of both spheres. Thus, I wouldn't fully agree with JimDeadlock's Review that it's "a puzzler through and through," since quite a few levels really do require "timing and dexterity."
The puzzley elements generally rely on how you use a sphere on one side of the board (e.g., left) to grab and use pickups that can influence the other side (e.g., right) and manipulate pitfalls. The main pitfalls are little sentinels whose line-of-sight-cones you need to avoid. If one of your spheres does get spotted by a sentinel, the sphere goes back to where it started -- which is actually used as part of the solution in a few levels.
So, for example, one of the pickups lets you send out a sort of sound-wave that distracts sentinels. If your left-sphere has this pickup and is standing in a "window" to the right side of the board, your left-sphere can clear a path on the right side to help your right-sphere through. Another pickup lets you open up "windows" in the first place. And so on. You can see how levels get complicated as you need to plan out the order in which to pick up and deploy pickups, on both sides of the board. (Each sphere can only carry 1 pickup at a time, and they're all single-use, but then re-spawn on the board where you found them).
There are 54ish levels, and while many of them offer a slow learning curve to learn new mechanics, the tougher ones can get pretty mind-bending as you work them out on the first playthrough. I think my first playthrough was ~2.5h total. Once you crack each level, they aren't too bad in retrospect, and so the 1 achievement you won't get in a normal playthrough (a speedrun achievement for beating the game in <35minutes in 1 sitting), is quite possible, though it took me a few tries -- especially since once you beat the last level, the game resets. No opportunity to practice the tough ones individually :(
There's supposed to be a story. I couldn't find it, but the user screenshots show that it does exist, so Idunno what happened in my case -- I doubt I missed much. The Settings/Options are a bit more filled out than in many games at the same price-point, and at time of writing, the Dev is active in the forums -- more than I can say for a lot of games, sadly.