After the creation of a wooden box controller, I decided to upgrade the design to a laser-cut acrylic box that contained LEDs which could be used to convey information to the player (such as player color). I used the facilities of the London Hackspace for most of the soldering and laser-cutting work.
Below are a few images from the process.
Frosted box color transition test:
Cutting the box sides from an acrylic sheet:
Testing multiple colors per Slider: