Working in partners, turn your phone into a device that creates a new form of interaction between you two. Think carefully about the type of interaction you want to have, rather than just what is technically possible. Make a quick prototype and then iterate repeatedly.
p5.js basics review
p5.js getting started info
Coding Train p5.js tutorials with Dan Shiffman
Getting Started with p5.js book (ebook and paperback)
Intro to programming for the Visual Arts online course (free)