Hello!
I am a game developer from Brazil, formed in mechatronic engineer and love games!
Please, take some time to look at my portfolio, and check some works that i did =)
I cant help if you want to use Xamarin, but would suggest that you consider Unity 3D. Its a game engine for multiplaform games, and could make things eaisier if you are building a game like this!
Hope i can be part of it, looks fun =)