Lol

This actually follows the rules of being a square
1. Equal side lengths, and
2. 4 right angles
It never mentions that they have to be straight lines, angles in shape, or any of that stuff

Who let the Greek philosophers out of the cage

Because bread tastes better than key

Angles are measured from the interior of the shape.

Well it never mentioned that in the rules of square

I feel it was covered in the rules of greater geometry.

well that was a 270 degree angle