For my project I wanted to build a piece of physically adapting hardware for learning a physical skill. In this case, balancing. I am part of a research project that has software to use sensors to determine performance and increases or decreases the difficulty depending on that performance.
The build of the board will have a transparent top to allow for various forms of feedback (e.g. vision/color) and an opaque bottom that houses all electronic and mechanics. The board has 2 slots at the end for pressure sensors (fail, the board hit the ground), slots for speakers (feedback), and a central area for the electronics hub and balance sensor (performance without failing, stability).
For this balance board, the difficulty has 2 ways to increase difficulty. It can increase the distance between guides or make the roller larger or smaller.
Small, unexpanded roller side view
Large, expanded roller side view