Hey,
There's definitely effort in this! I am a FPS gamer myself so seeing an FPS take on the theme is a good thing! There's occasional crashes with WebGL player, not sure why, didn't figure out any pattern and Itch.io client will not launch the game at all.
The wooden box thingy was very confusing as it felt like it was from a stealth game and this is about shooting(?). It worked all right fore sure, but it has absolutely no use in the game.
I also liked the idea of shooting through the screens, but it also made the game super easy? And it also made the game to feel like it's not a shooter per ce. Maybe this was the idea though?
I tried also to play it as a regular shooter and I know for a game jam a proper AI would take long to implement but it would have been awesome enemies would react to the player :)
Btw: Here's the crash capture. I think there's some floating vs integer conversions that causes the crash. 
I still think there' potential here and definitely one of the better ones all in all!
Good job and Cheers!