I love this! I have absolutely no idea why there weren't more (or any that I can find) games like this released during the gameboys' lifespan! I reckon you could have started a franchise back in the day.
Glad you like it 😊
To my knowledge there were not really any comparable games during the Game Boy's Lifespan. While there were some FPS like Faceball or Ray-Thunder, they were rather trying to emulate PVP experiences and had pretty clunky controls. Also, they did not have any level or upgrade system as far as I know. But they were still very impressive from a technical perspective.