tarting at 135 degrees and sweeping for 270 degrees
                new go.Shape({
                  name: 'SHAPE',
                  geometryString: 'M-70.7107 70.7107 B135 270 0 0 100 100 M0 100',
                  stroke: 'white',
                  strokeWidth: 4
                }),
                // three differently sized tick marks
                new go.Shape({
                  geometryString: 'M0 0 V10',
                  stroke: 'white',
                  strokeWidth: 1.5
                }),
    