SpheroGraph

Design presented to the sphero #make5000 contest.
The SpheroGraph allows the sphero to draw over a surface with a pen or a marker. The quality of the draw relies mostly on the ability to drive the sphero, ¡quite a challenge!. But the final idea would be fulfilled with an app that allows to scale the paper size, find the initial position of the sphero on it, and then make the sphero follow a fixed trajectory, maybe some words in cursive letters to make a big sign (it could be made with a finger over a touch screen).
To keep the design simple, the pen or marker should be tied to the frame with some rubber bands and its height should be adjusted.
The rod could be made of some metal rod of 3mm on diameter and glued to the frame so it get fixed and the wheel can rotate.