These GeoGebra files were part of my MAA MathFest 2016 talk
"Introducing Spacetime Geometry: Relativity on Rotated Graph Paper".
My slides are available here (at the website of the session organizer)
It describes aspects of my paper “Relativity on Rotated Graph Paper”, Am. J. Phys. 84, 344 (2016);
An informal introduction is presented at