I've drawn the attached sort of ST diagram to test my undersanding on how SR works. It intends to reflect a situation where: (i) B ship goes through A ship. (ii) Relative velocity is 0.5 c. (iii) When the left edge of both ships meet, both observers situated there send light signals to the other edge. (iv) Both signals reflect back on the other edge simultaneously. I would very much appreciate any spotting of mistakes in the calculations or any criticism on the way it is drawn. By the way, is this the Minkowsky or the Epstein-like style of diagram? And what would be here the spacetime interval on which both frames agree? Thanks in advance!