Blackboard
A blackboard (also known as a chalkboard) is a reusable writing surface on which text or drawings are made with sticks of calcium sulfate or calcium carbonate, known, when used for this purpose, as chalk. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone. Modern versions are often green because the colour is considered easier on the eyes.
The Theory of Tablet Orientation Relativity
Physics Joe HF Blackboard Relativity Lightcone Challenge Monochrome Greyscale
My attempt at a inverted tablet drawing. Using an old plug-in tablet, as inverting my Tablet PC...