docs: private void computeBitLocations() {
  		int N = numRows;
  		int row = N-1;
  		int col = N-1;
  		int direction = -1;
  
  		while (col > 0) {
  			if (col == 6)
  				col -= 1;
  
  			if (!get(row,col)) {
  				bits.add( new Point2D_I32(col,row));
  			}
  			if (!get(row,col-1)) {
  				bits.add( new Point2D_I32(col-1,row));
  			}
  
  			row += direction;
  
  			if (row < 0 || row >= N) {
  				direction = -direction;
  				col -= 2;
  				row += direction;
  			}
  		}
  	}