The game is completed and that is a testament. A few enemies with simple, easy to understand patterns which is good to familiarize the player with the game. The lack of exploration leaves a bit to be desired, and I would have loved reskinned enemies / tiles or something to spice up different areas, but the game is clear in its approach. The major gripe I have is the boss having too much health. It isn't extremely difficult, however janky hitboxes and huge healthbar make it a chore to kill, as I tried for 10 - 20 minutes straight basically and have been unable to kill it. I would say this boss is on the same tier of difficulty as some of the older nes games. The music was also pretty neat.
Otherwise, goodwork!