Hyper Rift

Hyper Rift is a choice-based interactive fiction for mobile platforms (Android, iOS, and perhaps also Windows Mobile). It's partly graphical -- you navigate between rooms using arrows on a map -- but almost all information is conveyed to you through text. The game is free, with some small ads in the bottom, and (I believe) the option to purchase an ad-free version if desired. I found the ads no distraction at all.

In Hyper Rift, we find ourselves waking up without memory in the medical bay of a spaceship full of horrors. So far so System Shock, but Hyper Rift is actually centered of saving and leading a large cast of NPCs. While these will mostly silently follow you to the point that they function more as inventory items, in certain situations they will do or say something that has a significant impact on the game. As you lead your (hopefully) growing band of equally amnesiac shipmates through the four levels of the spaceship, you will solve some mathematical puzzles and learn more and more about what was going on on the ship and what might be done to put things right.

Making everything come out in the optimal way seems to be a complex puzzle, requiring significant trial and error as well as careful exploration. From what I've seen, the puzzles have been carefully constructed; and there are more than ten different endings to be reached. While I'm personally not the kind of completionist who will search for them all, and while I'm also not motivated enough to try to get a better ending than my own (probably middle-of-the-road) ending L, I do think that there are many IF enthusiasts for whom this game can mean hours of fun. I certainly enjoyed the 2 to 3 hours I spent with it. Recommended.