diff --git a/mo_gymnasium/envs/mountain_car/__init__.py b/mo_gymnasium/envs/mountain_car/__init__.py
index f75fe751..523de281 100644
--- a/mo_gymnasium/envs/mountain_car/__init__.py
+++ b/mo_gymnasium/envs/mountain_car/__init__.py
@@ -6,3 +6,24 @@
     entry_point="mo_gymnasium.envs.mountain_car.mountain_car:MOMountainCar",
     max_episode_steps=200,
 )
+
+register(
+    id="mo-mountaincar-3d-v0",
+    entry_point="mo_gymnasium.envs.mountain_car.mountain_car:MOMountainCar",
+    max_episode_steps=200,
+    kwargs={"add_speed_objective": True, "merge_move_penalty": True},
+)
+
+register(
+    id="mo-mountaincar-timemove-v0",
+    entry_point="mo_gymnasium.envs.mountain_car.mountain_car:MOMountainCar",
+    max_episode_steps=200,
+    kwargs={"merge_move_penalty": True},
+)
+
+register(
+    id="mo-mountaincar-timespeed-v0",
+    entry_point="mo_gymnasium.envs.mountain_car.mountain_car:MOMountainCar",
+    max_episode_steps=200,
+    kwargs={"remove_move_penalty": True, "add_speed_objective": True},
+)
diff --git a/mo_gymnasium/envs/mountain_car/mountain_car.py b/mo_gymnasium/envs/mountain_car/mountain_car.py
index 6e88acca..0c2c5dbb 100644
--- a/mo_gymnasium/envs/mountain_car/mountain_car.py
+++ b/mo_gymnasium/envs/mountain_car/mountain_car.py
@@ -14,19 +14,50 @@ class MOMountainCar(MountainCarEnv, EzPickle):
     See [Gymnasium's env](https://gymnasium.farama.org/environments/classic_control/mountain_car_continuous/) for more information.
 
     ## Reward space:
-    The reward space is a 3D vector containing the time penalty, and penalties for reversing and going forward.
+    By default, the reward space is a 3D vector containing the time penalty, and penalties for reversing and going forward.
     - time penalty: -1.0 for each time step
     - reverse penalty: -1.0 for each time step the action is 0 (reverse)
     - forward penalty: -1.0 for each time step the action is 2 (forward)
+
+    Alternatively, the reward can be changed with the following options:
+    - add_speed_objective: Add an extra objective corresponding to the speed of the car.
+    - remove_move_penalty: Remove the reverse and forward objectives.
+    - merge_move_penalty: Merge reverse and forward penalties into a single penalty.
     """
 
-    def __init__(self, render_mode: Optional[str] = None, goal_velocity=0):
+    def __init__(
+        self,
+        render_mode: Optional[str] = None,
+        add_speed_objective: bool = False,
+        remove_move_penalty: bool = False,
+        merge_move_penalty: bool = False,
+        goal_velocity=0,
+    ):
         super().__init__(render_mode, goal_velocity)
-        EzPickle.__init__(self, render_mode, goal_velocity)
+        EzPickle.__init__(self, render_mode, add_speed_objective, remove_move_penalty, merge_move_penalty, goal_velocity)
+        self.add_speed_objective = add_speed_objective
+        self.remove_move_penalty = remove_move_penalty
+        self.merge_move_penalty = merge_move_penalty
 
-        self.reward_space = spaces.Box(low=np.array([-1, -1, -1]), high=np.array([-1, 0, 0]), shape=(3,), dtype=np.float32)
         self.reward_dim = 3
 
+        if self.add_speed_objective:
+            self.reward_dim += 1
+
+        if self.remove_move_penalty:
+            self.reward_dim -= 2
+        elif self.merge_move_penalty:
+            self.reward_dim -= 1
+
+        low = np.array([-1] * self.reward_dim)
+        high = np.zeros(self.reward_dim)
+        high[0] = -1  # Time penalty is always -1
+        if self.add_speed_objective:
+            low[-1] = 0.0
+            high[-1] = 1.1
+
+        self.reward_space = spaces.Box(low=low, high=high, shape=(self.reward_dim,), dtype=np.float32)
+
     def step(self, action: int):
         assert self.action_space.contains(action), f"{action!r} ({type(action)}) invalid"
 
@@ -39,11 +70,20 @@ def step(self, action: int):
             velocity = 0
 
         terminated = bool(position >= self.goal_position and velocity >= self.goal_velocity)
-        # reward = -1.0
-        reward = np.zeros(3, dtype=np.float32)
+
+        reward = np.zeros(self.reward_dim, dtype=np.float32)
+
         reward[0] = 0.0 if terminated else -1.0  # time penalty
-        reward[1] = 0.0 if action != 0 else -1.0  # reverse penalty
-        reward[2] = 0.0 if action != 2 else -1.0  # forward penalty
+
+        if not self.remove_move_penalty:
+            if self.merge_move_penalty:
+                reward[1] = 0.0 if action == 1 else -1.0
+            else:
+                reward[1] = 0.0 if action != 0 else -1.0  # reverse penalty
+                reward[2] = 0.0 if action != 2 else -1.0  # forward penalty
+
+        if self.add_speed_objective:
+            reward[-1] = 15 * abs(velocity)
 
         self.state = (position, velocity)
         if self.render_mode == "human":
diff --git a/pyproject.toml b/pyproject.toml
index 160f2b53..92b17de6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -23,7 +23,7 @@ classifiers = [
 ]
 dependencies = [
     "gymnasium>=0.28.1,<0.30",
-    "numpy >=1.21.0",
+    "numpy >=1.21.0,<2",
     "pygame >=2.1.0",
     "scipy >=1.7.3",
     "pymoo >=0.6.0",