diff --git a/challenges/octahedron.html b/challenges/octahedron.html
index 1aac7fb..8cbd597 100644
--- a/challenges/octahedron.html
+++ b/challenges/octahedron.html
@@ -8,6 +8,8 @@
 </head>
 <body>
 
+<a href="../">↩ Index page</a>
+
 <h1>Octahedron challenge</h1>
 <p>Can you create something like this using <a href="https://jsxgraph.org/docs/symbols/Point3D.html#constructor"><code>Point3D</code></a> and <a href="https://jsxgraph.org/docs/symbols/Polygon3D.html#constructor"><code>Polygon3D</code></a> elements? Don’t worry about including the colors; they’re just to emphasize how the polygons fit together.</p>
 <p>The <code>create</code> call for <code>Polygon3D</code> isn’t documented, but you can look at the polygon sampler for examples.</p>
@@ -129,5 +131,6 @@
     );
 }
 </script>
+
 </body>
 </html>
diff --git a/challenges/sphere-contours.html b/challenges/sphere-contours.html
index 56acd77..bdb1547 100644
--- a/challenges/sphere-contours.html
+++ b/challenges/sphere-contours.html
@@ -8,16 +8,14 @@
 </head>
 <body>
 
+<a href="../">↩ Index page</a>
+
 <h1>Sphere contour challenge</h1>
 <p>Can you create something like this using <a href="https://jsxgraph.org/docs/symbols/Sphere3D.html#constructor"><code>Sphere3D</code></a>, <code>Plane3D</code>, and <a href="https://jsxgraph.org/docs/symbols/IntersectionCircle3D.html"><code>IntersectionCircle3D</code></a> elements? Don’t worry about including the colors; they’re just to clarify what happens when you move the center of the sphere.</p>
 <p>The <code>visible</code> attribute will come in handy.</p>
 <p>Since the <code>create</code> call for <code>Plane3D</code> isn’t documented, I’ve included an <a href="#create-plane">example</a> below.</p>
 <div id="sphere-contours" class="jxgbox" style="width:600px; height:600px"></div>
 
-<h2 id="create-plane">How to create a 3D plane</h2>
-<p>A <code>Plane3D</code> is created from a base point and two vectors. The base point can be given either in coordinates or as a <a href="https://jsxgraph.org/docs/symbols/Point3D.html#constructor"><code>Point3D</code></a>. The vectors are given in coordinates.</p>
-<div id="plane-example" class="jxgbox" style="width:600px; height:600px"></div>
-
 <!-- a solution to the sphere contour challenge -->
 <script type="text/javascript">
 // to prevent variable name conflicts, we define variables locally using `let`
@@ -89,6 +87,11 @@
 </script>
 
 <!-- how to create a 3D plane -->
+
+<h2 id="create-plane">How to create a 3D plane</h2>
+<p>A <code>Plane3D</code> is created from a base point and two vectors. The base point can be given either in coordinates or as a <a href="https://jsxgraph.org/docs/symbols/Point3D.html#constructor"><code>Point3D</code></a>. The vectors are given in coordinates.</p>
+<div id="plane-example" class="jxgbox" style="width:600px; height:600px"></div>
+
 <script type="text/javascript">
 // to prevent variable name conflicts, we define variables locally using `let`
 // and put the code for each board in its own block
diff --git a/index.html b/index.html
index b79d3d2..6b56aa1 100644
--- a/index.html
+++ b/index.html
@@ -8,6 +8,8 @@
 </head>
 <body>
 
+<a href="../">↩ Writing list</a>
+
 <h1>A hands-on tour of some new 3D elements</h1>
 <p>These materials are from a <a href="https://jsxgraph.org/conf2024/program/fenyes/">short workshop</a> at the 2024 International JSXGraph Conference. You can watch a <a href="https://www.youtube.com/watch?v=gwc0BrLjuiI">video</a> of the workshop to learn more about how they were used. They’re available here, in a <a href="https://code.studioinfinity.org/Vectornaut/jsxgraph-3d-workshop">public Git repository</a>, and (for the templates) on JSFiddle.</p>
 
diff --git a/templates/circle-sampler.html b/templates/circle-sampler.html
index 958469e..ec3ca62 100644
--- a/templates/circle-sampler.html
+++ b/templates/circle-sampler.html
@@ -8,6 +8,8 @@
 </head>
 <body>
 
+<a href="../">↩ Index page</a>
+
 <h1>3D circle sampler</h1>
 
 <p>A <a href="https://jsxgraph.org/docs/symbols/Circle3D.html"><code>Circle3D</code></a> element is created from a center, a normal vector, and a radius. The center can be given either in coordinates or as a <a href="https://jsxgraph.org/docs/symbols/Point3D.html#constructor"><code>Point3D</code></a>. The normal vector is given in coordinates.</p>
diff --git a/templates/glider-sampler.html b/templates/glider-sampler.html
index 4b8d005..b02f6cb 100644
--- a/templates/glider-sampler.html
+++ b/templates/glider-sampler.html
@@ -8,6 +8,8 @@
 </head>
 <body>
 
+<a href="../">↩ Index page</a>
+
 <h1>3D glider sampler</h1>
 
 <!-- line glider -->
diff --git a/templates/intersection-sampler.html b/templates/intersection-sampler.html
index 930c31b..f07afea 100644
--- a/templates/intersection-sampler.html
+++ b/templates/intersection-sampler.html
@@ -8,6 +8,8 @@
 </head>
 <body>
 
+<a href="../">↩ Index page</a>
+
 <h1>3D intersection sampler</h1>
 
 <!-- plane-plane -->
diff --git a/templates/polygon-sampler.html b/templates/polygon-sampler.html
index 3d224b1..e47f20a 100644
--- a/templates/polygon-sampler.html
+++ b/templates/polygon-sampler.html
@@ -8,6 +8,8 @@
 </head>
 <body>
 
+<a href="../">↩ Index page</a>
+
 <h1>3D polygon sampler</h1>
 
 <!-- creating a polygon -->
diff --git a/templates/sphere-sampler.html b/templates/sphere-sampler.html
index 1ddc916..91131c8 100644
--- a/templates/sphere-sampler.html
+++ b/templates/sphere-sampler.html
@@ -8,6 +8,8 @@
 </head>
 <body>
 
+<a href="../">↩ Index page</a>
+
 <h1>Sphere sampler</h1>
 
 <!-- creating spheres -->
diff --git a/templates/view-demo.html b/templates/view-demo.html
index a17669f..60d35b2 100644
--- a/templates/view-demo.html
+++ b/templates/view-demo.html
@@ -8,6 +8,8 @@
 </head>
 <body>
 
+<a href="../">↩ Index page</a>
+
 <h1>View options demo</h1>
 
 <!-- central projection; depth ordering for points -->
