What determines whether you get a gem or not? Sometimes you get spawned inside of the cage, can collect it and get out, sometimes you land underneath and you can't get inside. There doesn't seem to be a clear pattern.

>>11865952 (OP)
I think it's random

Gonna bump so that I know for when I do seriously sit down and try not to die at Adventure Island.

Most likely it'll be a secret counter, like the "choose an egg" room
https://www.youtube.com/watch?v=Ux8ISs3R33Q