Thank you for the information good sir. When I say "fan game", I really mean, "game inspired by". Not using any of the game's assets, just a similar style using all my own assets.

My code-fu isn't up to writing my own engine at the moment. I've never really made a game before, beyond text adventures, so I haven't done anything graphical before. I'll take your advice to be look into existing free game engines and go from there, with a focus on Unreal and Unity. Thank you again.