A board with 11 x 11 squares. Arnold has a marker which initially is located in the middle square. In each move he can go one step vertically or horizontally. Arnold starts.
Bill's task is to stop Arnold. In each move he places a wall along a side of any of the squares. Arnold is not allowed to go through a wall.
Arnold wins if he can escape the board. Bill wins if he can stop Arnold from escaping. Given that both play in an optimal way, who will win?
Below you can try yourself.