I think that the game is very interesting in one player mode, 'cause the clever design lets you clear the levels even without having someone to play with... And that's a feature for me! This way you can play the game with a different approach: in two players mode you can walk around without worrying too much, while in single player you have to be careful and put your hands on the keyboard in certain ways in order to overcome the challenges. This reminds me of Zelda Triforce Heroes, where the one-player version of the game was harder than the multi, but still beatable! :D