Some years ago, I read a post on HN where someone made a text-mode game(? or something similar?) available through SSH. People could play the game by opening an SSH session and play from their terminals. This was non-trivial, and they explained all the ways they configured sshd to prevent players from running binaries other than the game.

I didn't bookmark that post, and I haven't been able to find it again to my great dismay. If anyone remembers this post and still has it, I'd love to read it again.