Light Clock Diamond (robphy) - v0.5

This is a visualization of the Light Clock Diamond based on my paper "Relativity on Rotated Graph Paper" (Am. J. Phys. 84, 344 (2016); http://dx.doi.org/10.1119/1.4943251 ) which is briefly described in "Spacetime Diagrams of Light Clocks" https://www.physicsforums.com/insights/spacetime-diagrams-light-clocks/