I had successfully done this with 5 different shapes, when I got to the yellow hectagon.
It didn't work.
The triangle, square, and diamonds worked. Even the red one worked (what's it called?). But the yellow shape, wouldn't do the trick.
I thought I had discovered some secret "rule of four". After all, I was taught to scientifically prove something, you have to do it 3 times and get the same results. I had FIVE positive tests, and ONE negative.
I'm just glad I did that sixth test before making a fool out of myself ;-)
But why won't it work?
Is there some mathamatical formula or rule?