Slices highlighting the properties of shocks in and around the star cluster. (a) Individual stellar winds reach Mach numbers of M_S ~ 100 and the cluster wind has M_S ~ 10. The transonic sheets, which are found downstream of the cluster-wind termination shock, have M_S ~ 1–2. (b) The flow is highly super-Alfvénic, except in a small number of localised regions in the superbubble and cluster core. (c) The cluster-wind termination shock is compressive across its entire surface, as shown by the negative divergence of the velocity field. Alternating compression and rarefaction zones inside the transonic sheets indicate a structure similar to that seen in the ‘shock diamond’ phenomenon. The values have been normalised to the maximum. Panels a and b show a z-axis slice of cluster I at 330 kyr. Panel c shows the same slice at 200 kyr.