Thymio in Playground - pen

Created by: ddoak

Using a pen (to create a trail) with Thymio is a very useful activity in teaching.

The current thymio simulation supports reading from the ground texture (bottom IR proximity sensors) - it could be interesting to record a pen trail in simulation by writing to an additional overlaid (rgba) texture or to a copy of the ground texture.

(this would make it possible to begin to simulate activities such as the "ant like behaviour" https://www.thymio.org/creations-en:navigation-fourni where the thymio senses modifications it has made to its environment)

A simple data switch to enable the pen in the playground file would avoid the need for additional interface.

(fully adding pen commands (up, down, width, colour) would be interesting but would add complexity and deviate from a direct simulation of the physical robot).