I love metroidvania games! This controls quite smoothly, and you gave me some time to get used to the controls before fighting monsters.
It would have liked to aim the gun upwards to hit enemies, like in Metroid.
I also would have liked to see something more original. It's one thing to be inspired by a game in a specific genre and another to copy it. I think you would have gained more experience in game design had you decided to take elements from Metroid but ultimately make your own thing.