One-dimensional density profile along the merger axis for DM (solid) and galaxies (dashed) at various times, as indicated. The top panel shows the evolution before the first pericentre passage, and the middle panel shows it shortly afterwards. In the bottom panel, the evolution following the first apocentre passage is displayed. The hSIDM scheme allows us to simulate a cluster merger for the strongly anisotropic Møller cross section with r = 10⁴. We validate this approach by noting that the results are (practically) independent of the choice of the critical angle, for θ_c ∈ {0.1,  0.3} (blue and orange curves, respectively). The full time evolution movie is available online.