I really liked the concept of the game. It was fun to have to use an external object to fight with rather than a gun or something like that and the way the fights played out like a puzzle was great! I got to task 7 and every time I tried to push the box at some point it ended up disappearing, not entirely sure why. I don't know if it was a collision issue with the walls or something like that. Also, I think the direction the box is pushed should be linked to the direction the player is pressing on the keyboard, rather than...whatever it is (I couldn't entirely figure out what the causation chain was).
Having said all that, the idea is good and if it were expanded on and polished up it could be a really interesting game. Great job!