Hello! I am working to reveal this shape/outline via a mask ...specifically the rectangle shape, as it animates via motionPath the shape should reveal. This pen is set up to show the rectangle animating along its path (.path2) successfully, but when I place it within a mask ("theSquare"), motionPath breaks. Commenting in <defs> and <mask> within the linked pen will replicate the error.   Can you help me understand why this is happening?  Thank You!