what does the "special shapes" option do?

[zedmango]

One of the setup options is "special shapes" and the choices are none, squares, triangles, and both.

I can't figure out what this does, and it does not seem to be explained anywhere. I've looked through all the help and can't find it.

Please help me figure out what this does!

[Romain672]

It add in the elements on the left some triangle, squares, both of them, or none of them.

[Tof63]

You'd better to test triangles in solo mode first, they add some difficulties