Interesting game, I actually enjoyed playing it! :) I have some small complaints however. I don't really like the font you used since it is too hard to read. You should be able to find other pixelated fonts that have a grater level of detail, so you can read them easier. Also, it seems like you can play the game only in fullscreen. Here is how it looks like if I don't make the game fullscreen: 
While the controls weren't bad (I mean what could be bad with such simple controls), I feel like there was no need to be able to move your mouse all around the screen, since all you are doing is changing the angle. So what I was thinking about is that you could make it so you can move the cursor only in a circle movement. For example, you could only move the cursor on the outline of the red circle (so not inside the circle and not outside the circle): 
instead of the whole screen. However I did not finish the game so there may be a reason for being able to move the mouse on the entire screen. Also, this is just an idea (which may not be that great in practice, I don't know), you can keep it the way you want :).