docs: improve docs

docs/source/envs/envs.rst

@@ -21,24 +21,28 @@ Gym environments that are based on Biological systems.
 Classic control environments
 ----------------------------
 
-Environments for classical control theory problems.
+Environments that are based on the `classical control gymnasium environments`_.
 
 .. toctree::
     :maxdepth: 1
 
     ./classic_control/ex3_ekf.rst
     ./classic_control/cartpole_cost.rst
 
+.. _`classical control gymnasium environments`: https://gymnasium.farama.org/environments/classic_control
+
 Mujoco environments
 -------------------
 
-Environments that are based on the MuJoCo physics engine.
+Environments that are based on the `mujoco gymnasium environments`_.
 
 .. toctree::
     :maxdepth: 1
 
     ./mujoco/swimmer_cost.rst
 
+.. _`mujoco gymnasium environments`: https://gymnasium.farama.org/environments/mujoco
+
 Robotics environment
 --------------------
 

examples/use_stable_gym.py

@@ -3,10 +3,10 @@
 
 import stable_gym  # noqa: F401
 
-ENV_NAME = "Oscillator-v1"
+# ENV_NAME = "Oscillator-v1"
 # ENV_NAME = "Ex3EKF-v1"
 # ENV_NAME = "CartPoleCost-v1"
-ENV_NAME = "Swimmer-v4"
+ENV_NAME = "SwimmerCost-v1"
 
 if __name__ == "__main__":
     env = gym.make(ENV_NAME, render_mode="human")

stable_gym/envs/mujoco/swimmer_cost/README.md

@@ -5,7 +5,7 @@
 </div>
 </br>
 
-An actuated two-jointed swimmer. This environment corresponds to the [Swimmer-v2](https://gym.openai.com/envs/Swimmer-v2/) environment included in the OpenAI gym package. It is different in the fact that:
+An actuated two-jointed swimmer. This environment corresponds to the [Swimmer-v4](https://gymnasium.farama.org/environments/mujoco/swimmer) environment included in the [gymnasium package](https://gymnasium.farama.org/). It is different in the fact that:
 
 *   The objective was changed to a speed-tracking task. To do this, the reward is replaced with a cost. This cost is the squared difference between the swimmer's forward speed and a reference value (error).
 

stable_gym/envs/mujoco/swimmer_cost/swimmer_cost.py

@@ -20,7 +20,7 @@ class SwimmerCost(SwimmerEnv):
 
     Source:
         This is a modified version of the swimmer Mujoco environment in v0.28.1 of the
-        :gymnasium:`gymnasium library <envs/mujoco/swimmer>`. This modification was first
+        :gymnasium:`gymnasium library <environments/mujoco/swimmer>`. This modification was first
         described by `Han et al. 2020 <https://arxiv.org/abs/2004.14288>`_. Compared to the
         original Swimmer environment in this modified version:
 
@@ -31,7 +31,7 @@ class SwimmerCost(SwimmerEnv):
         The rest of the environment is the same as the original Swimmer environment. Below,
         the modified cost is described. For more information about the environment
         (e.g. observation space, action space, episode termination, etc.), please refer
-        to the :gymnasium:`gymnasium library <envs/mujoco/swimmer>`.
+        to the :gymnasium:`gymnasium library <environments/mujoco/swimmer>`.
 
     Modified cost:
         .. math::