Well, I know what you mean. That foward and backward arm spinning is quite difficult. I used to practice it, and it comes naturally. The best way is to concentrate deeply on the movement of one of your arms, then adding the other very slowly.
There are many different brain teasers. But I guess that every move "unlocks" another. Only because of foward and reverse movements. If you get the foward down, it will unlock a new move if you reverse it.
As for the complexity of unlocking, I'm not sure where the unobvious kicks in. For example, when you're in the middle of spinning, stop, and see if you can spin in that same stance with balanced planes. I tried doing it on the windmill for my first try, it was surprisingly difficult for some reason. Try spinning one poi in the front of your head, and one in the back, and keep the planes completely even, and maintain your split time spinning. Its quite annoying at first.
That is probably the only way I think a poi move could unlock another. But I'm not too sure.. Just my thoughts though
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