Hmm not sure, I think the thought was the navigator shouldn't have to clear the grid before it moved something, the rover should do it automatically but that does increase the coupling between the rover and the grid so I'll move it to the navigator class.  As for the @grid.available? I'll try to move those out if they don't make the navigator class do too much.  Then the rover class will be fully decoupled from the grid class :smiley: