It’s called Bloxorz. Using your arrow keys, you have to manipulate the rectangular block so that it fits through a square-shaped hole. It’s pretty fun, and there are a few other elements that make it stay interesting, like collapsible bridges and orange tiles that can’t hold the block when it’s standing on end.
It kinda reminds me of that scene in Resident Evil: Extinction where the one zombie that’s becoming tame is playing with childhood games and remembering how to use a camera. He’s putting shapes into one of those hollow blocks with holes and looking kinda happy about it, but then he can’t get one of the shapes into an improper hole, so he turns back into a wild zombie and kills everybody who’s in the room with him. But this game isn’t that frustrating at all. In fact, I feel more like that zombie when I’m playing a little round of Mahjongg Solitaire.