@grid[$dimension / 2 - 1][$dimension / 2] = 1; @grid[$dimension / 2 - 1][$dimension / 2 + 1] = 1; @grid[$dimension / 2][$dimension / 2] = 1; @grid[$dimension / 2][$dimension / 2 - 1] = 1; @grid[$dimension / 2 + 1][$dimension / 2] = 1;