Neat concept. Really nice, consistent art design. The level design is a bit simplistic - it's got a strong arcade feel to it (compared to the mission-based structure seen in something like hotline). In terms of gameplay, keeping stuff simple and avoiding RPG-style elements is a smart move. What i'm seeing here is too fast paced for that. If, however, you decide to build in that direction, go for more of a "downwell" direction with them. Great stuff. More enemy/weapon variety, environmental hazards would make for appropriate focus areas for new content. In terms of enemy design - adjusting the attack telegraphy and range of enemies is the right way to go about smoothing out your difficulty curve. I would love to see this, fully realized, on steam/mobile.