public static CGAffineTransform MakeRotation(float angle){
float cosAngle = Mathf.Cos (angle);
float sinAngle = Mathf.Sin (angle);
CGAffineTransform t = Make (cosAngle, sinAngle, -sinAngle, cosAngle, 0, 0);
return t;
}
public static bool IsIdentity(CGAffineTransform t){