Hello all.

	I was attempting to go through the tutorial over at JG.  However, it breaks down rather quickly:

    World addMorph:
        (PolygonMorph
         vertices: {50 at 50.200@200}
         color: Color red
         borderWidth: 20
         borderColor: Color red)

The only problem is, in the process a Rectangle gets instanciated, and Rectangle doesn't have a corner mutator, only an accessor.  So it breaks.

	Where would I find the difference between the 2.x & 3.x series images?  I assume that somewhere is a document explaining the differences, and that it would have listed that the corner mutator was removed, and possibly offer an alternative.

	Am I missing something?