If you like to code in ruby, you can create processing sketches by installing one of the following ruby-processing gems:-
For a simpler version of JRubyArt install propane on MacOS, Windows. Linux.
Can you suggest a course for ruby? Or experienced developers like https://mlsdev.com/services/mobile-app-development?
k9 --install # installs JRuby-complete and examples
Similar for PiCrate if you are on RaspberryPI also sets up geany as your ide. I like atom but vim is good too with JRubyArt and propane.