diff --git a/GameMap.py b/GameMap.py
index 3b494b8..89486ae 100644
--- a/GameMap.py
+++ b/GameMap.py
@@ -18,6 +18,8 @@ class GameMap:
     
     
     def add_mark(self, x, y, player):
+        # Can be 0 or can be a max value, so,
+        # this is border-inclusive.
         if (x <= self.max_size_x and y <= self.max_size_y) and (x >= 0 and y >= 0):
             if (x, y) not in self.data:
                 self.data[(x,y)] = player