Prevent snake from turning around directly.

snake/snake_state.py

@@ -9,3 +9,7 @@ class SnakeState:
         return SnakeSegment(center=self._get_next_pos(old_head.get_position(), old_head.get_radius()),
                             radius=old_head.get_radius(),
                             color=old_head.get_color())
+    
+    @property
+    def type(self):
+        return self.__class__

snake/snake_state_machine.py

@@ -16,8 +16,16 @@ class SnakeStateMachine:
             InputManager.RIGHT: SnakeRightMovementState()
         }
 
+        self.__input_ignore_dict = {
+            SnakeDownMovementState: InputManager.UP,
+            SnakeUpMovementState: InputManager.DOWN,
+            SnakeLeftMovementState: InputManager.RIGHT,
+            SnakeRightMovementState: InputManager.LEFT
+        }
+
     
     def update(self, user_input):
+        if user_input != self.__input_ignore_dict.get(self.__state.type, None):
             self.__state = self.__next_state_dict.get(user_input, self.__state)