+;; type = 2.
+;; -----------------------------
+;; |>>> O|
+;; -----------------------------
+;; type = 3.
+;; -----------------------------
+;; |O <<<|
+;; -----------------------------
+;; type = 4.
+;; -----------------------------
+;; | O |
+;; -----------------------------
+;; type = 5.
+;; -----------------------------
+;; | O|
+;; -----------------------------
+;; type = 6.
+;; -----------------------------
+;; |O |
+;; -----------------------------