I think the shooting mechanics need extra work; I felt there wasn't enough control over how high the player can jump, and so it was really difficult to aim my shots. I also felt that 45 degrees up/down was way too much of an angle to actually shoot with. The shotgun was a cool addition. Reducing the delay before the shotgun fires would help a lot, because the shotgun is already short-ranged and slow. It doesn't need another handicap. Enemies don't telegraph their attacks until the second area, so it's really hard to visually keep track of how close an enemy is to firing back at the player. The first boss had some projectiles that would spawn in on top of the player with no warning. On the subject of bosses: The second boss has a laser that follows the player... I think it's fine to have just a millisecond of telegraph (which is what you do), however the state of the boss doesn't change once it is firing this laser. Thus, I feel the player needs to be directly told precisely how to deal with this new boss-state. Learning boss patterns by memory is common, but the player has to be able to learn what the pattern actually is.
In all, a captivating visual art-style and it immediately intrigues the player into exploring this game. With some more explicit telegraphing to the player on what the objectives are and how exactly to complete them, I think this could be a super challenging title in a great way.
8/10