Maybe it is easy for me to tell the next but:
After playing 842 days and sending 7139 trains Barnspace at the moment is 2535.
I built all the CBs in my Town and the last animal enclosure for the Ant eater family (with 2x 266 building materials needed) is also ready.
The two animal families for which I (consciously!) will not buy an enclosure are the Porcupines and the Platypus.
Gentle note: before new Zoo in January of this year I had a complete Zoo. So I feel really with you who struggle with the needed amount of BM.
Sorry Twilight, to shake your world!
But you all get there in the end, just keep on sending trains
