diff --git a/grid.py b/grid.py
index e3f9c89..cac3a98 100644
--- a/grid.py
+++ b/grid.py
@@ -48,7 +48,7 @@ class Grid:
             self.__grid[pos] = not self.__default
 
     def set(self, pos: Coordinate, value: Any = True):
-        if value in OFF_STATES and pos in self.__grid:
+        if (value == self.__default or value in OFF_STATES) and pos in self.__grid:
             del self.__grid[pos]
         elif value not in OFF_STATES:
             self.__trackBoundaries(pos)
@@ -90,18 +90,10 @@ class Grid:
         return self.minX <= pos.x <= self.maxX and self.minY <= pos.y <= self.maxY
 
     def add(self, pos: Coordinate, value: Union[float, int] = 1):
-        if pos in self.__grid:
-            self.__grid[pos] += value
-        else:
-            self.__trackBoundaries(pos)
-            self.__grid[pos] = self.__default + value
+        self.set(pos, self.get(pos) + value)
 
     def sub(self, pos: Coordinate, value: Union[float, int] = 1):
-        if pos in self.__grid:
-            self.__grid[pos] -= value
-        else:
-            self.__trackBoundaries(pos)
-            self.__grid[pos] = self.__default - value
+        self.set(pos, self.get(pos) - value)
 
     def getActiveCells(self):
         return [i for i in self.__grid.keys()]