diff --git a/tools/grid.py b/tools/grid.py
index 050f651..5c2b98e 100644
--- a/tools/grid.py
+++ b/tools/grid.py
@@ -5,6 +5,7 @@ from typing import Any, List, Union
 
 OFF = False
 ON = True
+Numeric = Union[int, float]
 
 
 class GridTransformation(Enum):
@@ -58,19 +59,31 @@ class Grid:
 
         return value
 
+    def add(self, pos: Coordinate, value: Numeric = 1) -> Numeric:
+        return self.set(pos, self.get(pos) + value)
+
+    def sub(self, pos: Coordinate, value: Numeric = 1) -> Numeric:
+        return self.set(pos, self.get(pos) - value)
+
+    def mul(self, pos: Coordinate, value: Numeric = 1) -> Numeric:
+        return self.set(pos, self.get(pos) * value)
+
+    def div(self, pos: Coordinate, value: Numeric = 1) -> Numeric:
+        return self.set(pos, self.get(pos) / value)
+
     def get(self, pos: Coordinate) -> Any:
         if pos in self.__grid:
             return self.__grid[pos]
         else:
             return self.__default
 
-    def getOnCount(self):
+    def getOnCount(self) -> int:
         return len(self.__grid)
 
     def isSet(self, pos: Coordinate) -> bool:
         return pos in self.__grid
 
-    def getCorners(self):
+    def getCorners(self) -> List[Coordinate]:
         if not self.mode3D:
             return [
                 Coordinate(self.minX, self.minY),
@@ -100,16 +113,10 @@ class Grid:
         else:
             return self.minX <= pos.x <= self.maxX and self.minY <= pos.y <= self.maxY
 
-    def add(self, pos: Coordinate, value: Union[float, int] = 1) -> Union[float, int]:
-        return self.set(pos, self.get(pos) + value)
-
-    def sub(self, pos: Coordinate, value: Union[float, int] = 1) -> Union[float, int]:
-        return self.set(pos, self.get(pos) - value)
-
-    def getActiveCells(self):
+    def getActiveCells(self) -> List[Coordinate]:
         return list(self.__grid.keys())
 
-    def getSum(self, includeNegative: bool = True):
+    def getSum(self, includeNegative: bool = True) -> Numeric:
         grid_sum = 0
         for value in self.__grid.values():
             if includeNegative or value > 0:
@@ -129,8 +136,7 @@ class Grid:
         else:
             return [x for x in neighbours if self.get(x) != self.__default]
 
-    def getNeighbourSum(self, pos: Coordinate, includeNegative: bool = True, includeDiagonal: bool = True) \
-            -> Union[float, int]:
+    def getNeighbourSum(self, pos: Coordinate, includeNegative: bool = True, includeDiagonal: bool = True) -> Numeric:
         neighbour_sum = 0
         for neighbour in pos.getNeighbours(
             includeDiagonal=includeDiagonal,