Like the others said before, the collisions are pretty wonky and the bullet often goes in the wrong direction and the movespeed is way too slow.
Fun game though, it's a nice blend of puzzler and shooter but the level design could be improved a lot, right now it's pretty unforgiving and I'm stuck on level 7 since the bullet often ends up in a bad position.
I would like to see the shooter aspect of it being expanded more, maybe make it more frantic with more aggressive enemies ala Hotline Miami.
Also, you should use preload() instead of load() for switching scenes so that there's no delay when loading levels and menus.