public void act()
    {
        Grid<Actor> gr = getGrid();
        for(int r = gr.getNumRows() - 1; r >= 0; r--)
            for(int c = gr.getNumCols() - 1; c >= 0; c--)
            {
                Actor a = (Actor)gr.get(new Location(r, c));
                if(a != null) {a.removeSelfFromGrid();}
            }
    }