@stared Great game, much appreciated! I have a question about level 20. If I put a sugar glass behind the laser and then two directly at the two outputs of the PBS, it doesn't work (interference triggers the bomb). If I move the two sugar glasses after the PBS behind the two respecitive mirrors next in each path (so the paths become Laser->SG->PBS->Mirror->SG in each arm), the interference works correctly and I pass the level. I just can't wrap my head around why the phase is different in each case. It would be really helpful to be able to inspect the quanta at each point in time so you can see how each element affects phase and polarization exactly.