Made documentation for carracing more descriptive, and renamed one of…

… the variable names (#2755)

gym/envs/box2d/car_racing.py

@@ -62,7 +62,7 @@ def _contact(self, contact, begin):
             return
 
         # inherit tile color from env
-        tile.color = self.env.norm_road_color / 255
+        tile.color = self.env.road_color / 255
         if not obj or "tiles" not in obj.__dict__:
             return
         if begin:
@@ -132,7 +132,7 @@ class CarRacing(gym.Env, EzPickle):
     In this scenario, the background and track colours are different on every reset.
 
     ### Version History
-    - v1: Current version (0.24.0)
+    - v1: Change track completion logic and add domain randomization (0.24.0)
     - v0: Original version
 
     ### References
@@ -196,7 +196,7 @@ def _destroy(self):
     def _init_colors(self):
         if self.domain_randomize:
             # domain randomize the bg and grass colour
-            self.norm_road_color = self.np_random.uniform(0, 210, size=3)
+            self.road_color = self.np_random.uniform(0, 210, size=3)
 
             self.bg_color = self.np_random.uniform(0, 210, size=3)
 
@@ -205,7 +205,7 @@ def _init_colors(self):
             self.grass_color[idx] += 20
         else:
             # default colours
-            self.norm_road_color = np.array([102, 102, 102])
+            self.road_color = np.array([102, 102, 102])
             self.bg_color = np.array([102, 204, 102])
             self.grass_color = np.array([102, 230, 102])
 
@@ -365,7 +365,7 @@ def _create_track(self):
             t = self.world.CreateStaticBody(fixtures=self.fd_tile)
             t.userData = t
             c = 0.01 * (i % 3) * 255
-            t.color = self.norm_road_color + c
+            t.color = self.road_color + c
             t.road_visited = False
             t.road_friction = 1.0
             t.idx = i