This design shows how to create a correct reflection tool for the heptagon field.
That field uses an embedding, a linear transformation to make heptagons look regular. The underlying vectors over the heptagon field cannot construct regular heptagons, but they can faithfully represent order-7 rotation transformations, and the associated reflections. (Yes, this is surprising.)
The default reflection tool is implemented using a naïve dot-product formula that doesn’t work. The solution is to construct two (apparently) orthogonal reference frames, and use the linear map tool factory to construct a reflection mapping.
