Tri: scale up by 2/3*sqrt(3)

Scaling by 2/3*sqrt(3) makes the width of a single triangle 1.0, which
is roughly inline with all the other shapes.

This should make the text & edges look more consistent across board
types.
Square: scale side length by 0.8

The squares are now "smaller", so that edges and text should be more
visible (by being correspondingly larger).