Rapid Interface Prototyping

BeatBearing is a tangible music sequencer driven by ball bearing placement.

A nearly equivalent system could be prototyped using a laptop screen and an overhead webcam. The screen would provide the "current position" line, and the camera would read the content. The main problem is obstruction, but there are better approximations (adding more cameras, mirrors, or assuming permanence for obstructed regions).

Furthermore, by removing the material constraint (i.e., ball bearings), we open up a number of possibilities. Multicolored jelly bean-based edible/tangible interfaces, anyone?

Update: I worked this one out, but with Skittles instead of jellybeans.