Spirits of Xanadu
If you like mystery, exploration, and psychological horror, this is a wonderful way to spend 3 hours. (More, if you want to take the time to earn some of the achievements.)
The story has themes and tone reminiscent of Solaris (especially Tarkovsky's film adaptation), and also The Quatermass Experiment. Both are excellent reference points.
There are some good puzzles in the game, that are not impossible to solve if you are patient. The ship is small enough that you won't feel frustrated with going back to look for clues you might have missed.
I'd also like to thank the developer for supporting Linux!