Very nice pace, great gameplay idea implementation. 

Boss behaviour surprised the most. 

Floating yellow 2d particle-quads making enemies hard to spot at some times, a most at the second biome, after first boss fight. 

Very nice coding, not a single bugs spotted, nothing crashed. Runs pretty very well on 2016's 1060 6. 

Verdict : Super fine playable proof of concept. If refine it a bit with better enemies models and animations it could be perceived well as the quite nice indie project.

P.S. on Sata2 sdd it's loading with a rainbowdash speed!