Graphics are great, nice pixel art and filters.
I liked the audio, it went along with the theme and generated a good tense ambience.
The difficulty is a little high but with enough patience and getting used too, can be completed. I had some trouble using the middle mouse but it think it has more to do with my mouse wheel, which was getting trouble with the Unity interface and the web explorer. The zoom mechanic was a little difficult but you get used to it.
I don't know if it was planned, but is more difficult to encounter enemies on vertical pathways than horizontal because of the screen size. At vertical, enemies can shoot you from the edge of the screen, which give very little time to react.
Overall really good job.
Also, I found a little bug:
- When played a second time after finishing, the character no longer moves. This can be reproduced, it happened me twice under same conditions for both hardmode and easy mode.