Hello there, Noahlint403! Unorthodox choice for a first post, but OK. Introduce yourself
over in this forum, please.
I think your first step is to learn about coding for the Gamebuino. If you know C++, it shouldn't be too hard, as the code has a C++-like syntax. Click
here to learn how to learn, and
here and
here for all Arduino and Gamebuino commands and what they do. Ask on the forums if you're stuck anywhere!
Your next step is to figure out exactly what type of game you want to make. I see ways that your concept could be a platformer-shooter, a vertical-scrolling shooter, a side-scrolling shooter, a rail-shooter, a FPS (and I bet it could fit in other genres than shooter). Maybe it could be a combination of all of them. I think you should have more of an idea of the genre before any one of us continues.
Oh, and I will gladly help you. I'm kind of a beginner as well; it'll be a learning process for the both of us
Hope this helped!