diff --git a/cell.py b/cell.py
index 80f4ecc..a5d4c87 100644
--- a/cell.py
+++ b/cell.py
@@ -8,9 +8,17 @@ class CellWall:
     a Cell's wall.
     """
 
-    def __init__(self, line: Line) -> None:
+    def __init__(self, line: Line, window: Window) -> None:
         self.exists = True
         self.line = line
+        self._window = window
+
+    def draw(self):
+        fill_colour = self._window.cell_grid_colour
+        if not self.exists:
+            fill_colour = self._window.background_colour
+
+        self._window.draw_line(self.line, fill_colour=fill_colour)
 
 
 class Cell:
@@ -46,10 +54,10 @@ class Cell:
         right_wall = Line(Point(x2, y1), Point(x2, y2))
 
         self._walls: Dict[int, CellWall] = {
-            Cell.TOP_WALL: CellWall(top_wall),
-            Cell.BOTTOM_WALL: CellWall(bottom_wall),
-            Cell.LEFT_WALL: CellWall(left_wall),
-            Cell.RIGHT_WALL: CellWall(right_wall),
+            Cell.TOP_WALL: CellWall(top_wall, window),
+            Cell.BOTTOM_WALL: CellWall(bottom_wall, window),
+            Cell.LEFT_WALL: CellWall(left_wall, window),
+            Cell.RIGHT_WALL: CellWall(right_wall, window),
         }
 
         # Calculate the cell's central point
@@ -85,10 +93,10 @@ class Cell:
 
     def wall_exists(self, wall: int) -> bool:
         if wall not in self._walls:
-            raise Exception("received invalid cell wall")
+            raise CellInvalidWallError(wall)
         return self._walls[wall].exists
 
-    #def break_walls_r(self, i: int, j: int) -> None:
+    # def break_walls_r(self, i: int, j: int) -> None:
     #    self.visited = True
     #    while True:
     #        list_i = []
@@ -102,49 +110,8 @@ class Cell:
         if not self._window:
             return
 
-        if self.wall_exists(Cell.TOP_WALL):
-            self._window.draw_line(
-                self._walls[Cell.TOP_WALL].line,
-                fill_colour=self._window.cell_grid_colour,
-            )
-        else:
-            self._window.draw_line(
-                self._walls[Cell.TOP_WALL].line,
-                fill_colour=self._window.background_colour,
-            )
-
-        if self.wall_exists(Cell.BOTTOM_WALL):
-            self._window.draw_line(
-                self._walls[Cell.BOTTOM_WALL].line,
-                fill_colour=self._window.cell_grid_colour,
-            )
-        else:
-            self._window.draw_line(
-                self._walls[Cell.BOTTOM_WALL].line,
-                fill_colour=self._window.background_colour,
-            )
-
-        if self.wall_exists(Cell.LEFT_WALL):
-            self._window.draw_line(
-                self._walls[Cell.LEFT_WALL].line,
-                fill_colour=self._window.cell_grid_colour,
-            )
-        else:
-            self._window.draw_line(
-                self._walls[Cell.LEFT_WALL].line,
-                fill_colour=self._window.background_colour,
-            )
-
-        if self.wall_exists(Cell.RIGHT_WALL):
-            self._window.draw_line(
-                self._walls[Cell.RIGHT_WALL].line,
-                fill_colour=self._window.cell_grid_colour,
-            )
-        else:
-            self._window.draw_line(
-                self._walls[Cell.RIGHT_WALL].line,
-                fill_colour=self._window.background_colour,
-            )
+        for _, wall in self._walls.items():
+            wall.draw()
 
     def draw_move(self, to_cell: 'Cell', undo: bool = False) -> None:
         """
@@ -161,6 +128,20 @@ class Cell:
         self._window.draw_line(line, fill_colour)
 
 
+class CellInvalidWallError(Exception):
+    """
+    CellInvalidWallError is raised when the program tries to specify a Cell's
+    Wall that does not exist.
+    """
+
+    def __init__(self, wall: int, *args):
+        super().__init__(args)
+        self.wall = wall
+
+    def __str__(self):
+        return f"Invalid Cell Wall (wall int: {self.wall}) specified."
+
+
 class CellInvalidError(Exception):
     """
     CellInvalidError is raised when the program tries to create a Cell whose
diff --git a/tests.py b/tests.py
index e5ddcce..c023349 100644
--- a/tests.py
+++ b/tests.py
@@ -1,5 +1,6 @@
 import unittest
 from maze import Maze
+from cell import Cell
 
 
 class Tests(unittest.TestCase):
@@ -55,9 +56,8 @@ class Tests(unittest.TestCase):
             2,
             2,
         )
-        self.assertFalse(maze._cells[0][0]._top_wall.exists)
-        self.assertFalse(
-            maze._cells[number_of_cell_rows - 1][number_of_cells_per_row - 1]._bottom_wall.exists)
+        self.assertFalse(maze._cells[0][0].wall_exists(Cell.TOP_WALL))
+        self.assertFalse(maze._cells[number_of_cell_rows - 1][number_of_cells_per_row - 1].wall_exists(Cell.BOTTOM_WALL))
 
 
 if __name__ == "__main__":