making new apps

[Lolboer9999999]

i was able to install opentom, i can play dune2 and all that but i have no clue on how to make my own programs and what the limitations for those would be, (i know a bit of java, c++ and python), the main thing i wanna do is to be able to connect it to an arduino to use it as an interface (just a screen with a few buttons would do)
if anyone could help me get started that would be great cuz i have no clue how to do this