Oof, I don't like that Matrix3x2 type. "It's a 3x2 matrix, but we're going to pretend it has a last column going 0/0/1 so we can get a determinant or multiply them together, but when we negate or add or subtract them it's still going to be 0/0/1."

It's the classical representation of affine transforms (translate, rotate, scale, etc) using homogeneous coordinates.

https://en.wikipedia.org/wiki/Transformation_matrix#Affine_t...

Ah, thanks. I figured it might be something like this but the documentation is very dry and doesn't seem to mention it.