Reflection changes "left-right". So effectively, a sugar solution (rotating polarization) before mirror rotates it in the opposite direction (vs a sugar solution after a mirror).
Actually it is a tricky thing I realised while testing this game. I thought it was an error in code. But nope - it was how does physics work. :)
https://imgur.com/a/OkEQY
https://imgur.com/a/Byo8E