Releasing the mouse when it's out the window seems fine, but the code I wrote says that you can only initiate the impulse when the box is colliding with the world (not best design), that could explain why the clicks doesn't work sometimes, I'll look further into this to make the game better, thank you!
Interesting game, love the idea that the "how to play" page basically says: "just play and you will learn it", I got confused at the first two attempts but then it just clicked, really cool game!
