The art style and audio design fit the game you were trying to make very well. The problem for me is the execution of the main mechanic. While I did enjoy the drifty nature of the ship and the impact of the shots, I feel like the cannon firing on its own could have been improved upon.
Simply put, I feel like it fired too slowly. It just felt like there was a lot of time between shots and I was often just waiting for the ship to fire, rather than having to actively fight against the constraint. Powerups to make the ship fire faster, or different types of shot would have made this entry even stronger as it would feel like there was some progression, despite the out of control nature of the random firing.
While I did enjoy the game, it needed something to keep the player interested. A clear goal or a presented score could have done that.
I want to be clear that I did like the game, but there were jsut a few minor issues that stopped it from being amazing to me. If fixed, this game could be great.