I wonder how much the less versatile C3BO version costs to build. It seems to me that you could use a cheap MC, a grid of 10 solenoids, and a simple light senso

I wonder how much the less versatile C3BO version costs to build. It seems to me that you could use a cheap MC, a grid of 10 solenoids, and a simple light sensor to build a version that would work on most touch screens and not have to deal with the hassle of building a 2D plotter, integrating a webcam, and controlling it with a relatively expensive Arduino.