Draw tower to screen

classes/towers/tower.py

@@ -16,3 +16,11 @@ class Tower(object):
 
         if self.properties['surface'] is None:
             raise ValueError('Missing surface for tower')
+
+    def draw(self, screen):
+        screen.blit(
+            self.properties['surface'],
+            self.properties['surface'].get_rect()
+        )
+
+        return screen