The idea and game feel are great, and the two colour palette works very well with the concept! I was able to make it to the end, although I think I cheesed the final boss a bit by always standing on the edge and leaving the arena as soon as it started firing.
In terms of feedback, I was finding it challenging to dodge attacks in the smaller arenas especially when using weapons creating a lot of bullets like the shotgun since the bullets all look the same, so it was hard to tell my bullets apart from the enemy's.