Green squares mark draggable points which generate simple shear or pure shear strain.
You may draw a circle or measure length and orientation of a line using the Options menu. Click and drag each square and circular handle in turn and observe the effects. Drag the top square to one side and then move the circular handles vertically above and below the connected square handles. Click and drag either square handle and observe the effects on the card deck. The card deck is deformed by pure shear.