A really fun little experience!
The theme is really interesting, and the visual design as a whole flowed together extremely well. The first stage of the game was basically as good as it could be, however the second stage had a few issues for me.
I should start by saying that the idea for this stage is really, really good, and I was smiling throughout the whole thing my first time through, but I did find that it was really hard to perceive how close I was to the exit of the stage. Another thing I noticed was that the shots from the back of the level go through the edges of the barrels, so hiding behind some areas of them was ineffective. While the barrels issue can be solved by perhaps fixing up a few collision problems, I'm honestly unsure about the depth perception issue I found for me, but the concept for it as a whole is extremely impressive to begin with.
Really fun time, well done!