Got 39. The movement takes a bit to get used to, but works fine after that. It looked like the knife dropping had a rather drastic amount of random timing to it.
Some general design advice: I recommend having the menu of any game use the same type of controls as the gameplay itself. In this case, I'm best at using my right hand for both the mouse and the arrows, so the first thing I had to do after clicking to start the game was to quickly move my hand over to the keyboard.