Detect 2D FLIPS on the Z Axis

Hi,

So I have this 2D POGO, a stick basically, which hops around. How do I detect if it does a flip between hops?

Optionally, i would like to detect if it is a front/back flip and also if it was a single/double/triple/ etc.

I'm not sure what I have to do, I tried subtracting the last rotation from the current one and adding them. I get strange results and I don't know how to do this.

Thanks!