Rotating mirrored pyramids? Help/Ideas wanted.

Hi.

I've been trying to setup this certain model in grasshopper. It consist of equally--length-sized triangles. Whom are mirrored and rotate - and then build upon each other. 

The main problem is creating a method for rotating a particular triangle around it's own point. 

And the second problem is how to set it up, so that the definition could generate more triangles? - More triangles that are set up the same way as it predecessors. 

Please check the attached files for a more friendly explanation.