Well I don't want to repeat what everyone else has already said. This game reminds me of Zillion on the Master System so it's kinda nostalgic. I like the artstyle and general theme of the game. There's lots of potential here,
Also, I recommend looking into Zillion for the Master System. One thing that game had that I would recommend adding is the ability to crouch and crawl so you can shoot enemies at different heights. This could also be used for navigation.