The art is great. 

The gameplay has a few issues. Mainly the collision between your sub and projectiles. I'm going to assume you used squares, which might not have been the best choice. The other issue is your rate of fire. if the missile goes off screen, there's no telling when you'll get it back. A lot of time ends up just sitting there waiting for the missile to respawn. 

The actual controls were great. It felt good to move around and I like the missile hovering menacingly in stark contrast to the adorable sub. It's a great aesthetic.

really fun! cute art style, good gameplay, overall very good!