Nice submission! Definitely on theme.
The Level feels well put together, I can see a lot of effort went into getting that right. I personally liked the difficulty level and the fact that you have to upgrade your ship to progress.
Art style is cool. The backgrounds and vines in particular are great/walls are great. The music complements the art as well, which is good.
For improvements, I'd suggest you make it so that holding down the mouse lets you continuously shoot instead of having to click each time, and zooming out the camera so the player can see a bit more.
Additionally, I found a couple of bugs. One is the Background jitter, the other was that I could buy stuff even though I did not have enough money (only subtracted 2/3 for an item listed as >10).
Cool game. Great job!