Well---simple, addictive, greatly polished & themed.
The gameplay is a clever twist to the classic toy---it goes in the square hole. Everything. The movements from the holes added an unexpected amount of difficulty, and made the game really enjoyable. Also, I really loved the smoothness of motion from the holes, really enhancing the game's vibe.(I can't put it in words but like I just loved the way they moved) :)
PICO-8 allows some great pixel styled games with nice polishing to be created: although I haven't personally used it, but I have seen enough great games(like this one) in Trijams that had almost perfect polishing for the jam.
Great job!