docs: public double acuteAngle(  SquareNode a , int sideA , SquareNode b , int sideB ) {
  		Point2D_F64 a0 = a.square.get(sideA);
  		Point2D_F64 a1 = a.square.get(add(sideA, 1));
  
  		Point2D_F64 b0 = b.square.get(sideB);
  		Point2D_F64 b1 = b.square.get(add(sideB, 1));
  
  		vector0.set(a1.x - a0.x, a1.y - a0.y);
  		vector1.set(b1.x - b0.x, b1.y - b0.y);
  
  		double acute = vector0.acute(vector1);
  		return Math.min(UtilAngle.dist(Math.PI, acute), acute);
  	}