🚀 go-pugleaf

	In the model 400/800 machines (and probably in the XL's), you can
modify the display list to form custom screens.  You can actually see the
changes being made by POKEing new values into the current display list.
All except for the very last display list instruction which is a JUMP to
a two byte address which is the beginning of the display list.  (This way
you keep looping thru the same display list over and over to keep the
screen refreshed).
	My question is why doesn't changing the last instruction or address
have any effect?  I've even POKEd zeroes into the last three bytes of a
display list and seen no change to the screen.