Learned tech without having prerequisite #900
Description
Not sure how I managed to learn Metallurgy before learning Chemistry, but it seems there is a gap somewhere that we allow for this to happen.
This happened while I was in obvserver mode while having Metallurgy in my research queue. I remember seeing the count down, so it's not a glitch that I learned this instead of something else, it was allowed to be selected and reseached.
I can't manage to recreate it, and I have never seen this in a normal game.
