Funny and clever! Other than the collisions and walking speed, which others have pointed out, this is a really good game. Good job!

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.

Played on my laptop which has terrible input, so I couldn't move and quickly fire a shot if necessary, so I had to set up every shot carefully. From that perspective it's a cool puzzle game. Faster player movement would be nice, and like others have said the bullet can bounce strangely, more than a few times it came right back to me even though I shot it at an angle. Once it went straight through a wall. It's got that flash game fun factor

Consider faster movement speed, it's kinda unbearable

The enemy shot sound is so loud. Scared the shit out of me when they first started firing.  Seems like a solid ground for a puzzle game, perhaps have 3 difficulty modes:

Easy: Red line shows where bullet will bounce and end up

Normal: Red line only shows to first wall

Hard: No dot sight only reticle

It's a solid concept. I bet there's loads of interesting levels you could make out of this. I especially liked how you mixed things up with the shield guys.

This does remind me of some of the better golden-age flash games. My only complaint is that the bounce physics behave weirdly sometimes.