I'm glad to hear you enjoyed it, and I'm glad to hear your feedback on the aiming! I was trying to go for a niche control scheme that would have made the game standout from others "at the time." (Hopefully there would have been lots of playground chatter about this one!)
To develop this I used GB Studio, a really neat suite that's perfect for beginners, proof of concepts, or those on a time crunch (like game jams)! Definitely recommend it if you're trying to get into Game Boy development!