diff --git a/16_reinforcement_learning.ipynb b/16_reinforcement_learning.ipynb
index 15c258e..30f2ab2 100644
--- a/16_reinforcement_learning.ipynb
+++ b/16_reinforcement_learning.ipynb
@@ -574,6 +574,15 @@
     "    plt.show()"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "openai_cart_pole_rendering = False  # don't try, just use the safe way?"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 26,
diff --git a/docker/Dockerfile b/docker/Dockerfile
index 82da41f..72a16f2 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -6,12 +6,15 @@ RUN apt-get update && apt-get upgrade -y \
         build-essential \
         git \
         sudo \
+        cmake zlib1g-dev libjpeg-dev xvfb libav-tools xorg-dev libboost-all-dev libsdl2-dev swig \
     && rm -rf /var/lib/apt/lists/*
 
 RUN conda update -n base conda
 RUN conda install -y -c conda-forge \
         tensorflow \
-        jupyter_contrib_nbextensions
+        jupyter_contrib_nbextensions \
+        pyopengl
+RUN pip install "gym[atari,box2d,classic_control]"
 
 ARG username
 ARG userid
diff --git a/tools_numpy.ipynb b/tools_numpy.ipynb
index 5ec032d..ed2d81b 100644
--- a/tools_numpy.ipynb
+++ b/tools_numpy.ipynb
@@ -459,7 +459,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "NumPy first creates three `ndarrays` (one per dimension), each of shape `(3, 2, 10)`. Each array has values equal to the coordinate along a specific axis. For example, all elements in the `z` array are equal to their z-coordinate:\n",
+    "NumPy first creates three `ndarrays` (one per dimension), each of shape `(2, 10)`. Each array has values equal to the coordinate along a specific axis. For example, all elements in the `z` array are equal to their z-coordinate:\n",
     "\n",
     "    [[[ 0.  0.  0.  0.  0.  0.  0.  0.  0.  0.]\n",
     "      [ 0.  0.  0.  0.  0.  0.  0.  0.  0.  0.]]\n",