Logic Puzzle Sampler is not a game; it describes itself more accurately as a toy, and it is also a programming example that comes with Inform 6 source code. As a toy it will probably not hold your attention very long, but as a piece of Inform programming, it is worthy of respect -- and could perhaps even be useful, in a somewhat bizarre game.
Playing with Logic Puzzle Sampler consists in manipulating a SHRDLU-like world of blocks and balls, and writing sentences about this world on sheets of paper. If the sentences are true, the paper turns green; if they are false, the paper turns red. Of course, the game accepts only a very limited set of sentences, but this is still impressive.
Even more impressive is the fact that you can write sentences about the colours of the pieces of paper themselves. And yes, this does allow you to have some self-referential fun -- luckily, Logic Puzzle Sampler has not restricted itself to a two-valued logic!
As the about-text indicates, the model beneath the toy is somewhat limited, and doesn't always analyse the situation perfectly. (Spoiler - click to show)For instance, if A says "B is green"; B says "C is green"; and C says "B is red"; the game will correctly turn B and C grey, but it will then incorrectly turn A grey as well, while it should simply be red. Still, what it can do is striking and well worth a look for those who are interested in such things.