I have been testing some Perspex elements with triangular cut-outs recently and they are surprisingly good to use.

The ones that I am playing with are "home made" from 3mm Perspex and I have tried them with just the equilateral triangle shape cut in them.

On some I have used a countersink bit on the reverse side to give the effect that the triangle is "floating" in space and this is helped by the thickness of the Perspex that was used to make them from..

The one without a countersink allows you to see more of the surrounding area better but the one with the countersink tends to make it easier to focus on "the black bit" more easily.

I have yet to try any of the other shapes that have been mentioned such as square or even diamond cut-outs but that fact that anything that is not circular actually works really has come as a great surprise.

I wonder who it was that had the foresight to first experiment with the idea of having odd shaped cut-outs in a foresight element ? - whoever it was did a good job and now we can experience it too.