diff --git a/01.courses/01.optics/03.the-nature-of-light/03.annex/annex.fr.md b/01.courses/01.optics/03.the-nature-of-light/03.annex/annex.fr.md
index d75a697a3..a8203417c 100644
--- a/01.courses/01.optics/03.the-nature-of-light/03.annex/annex.fr.md
+++ b/01.courses/01.optics/03.the-nature-of-light/03.annex/annex.fr.md
@@ -5,12 +5,28 @@ slug: annexe
 
 ## Annexe
 
+### Tests
+
 La [Constante $c$](#une-constante-fondamentale-de-la-nature-la-vitesse-de-la-lumière).
 
+
+[Current chapter](.)
+
+[Parent chapter](..)
+
+[Sibling chapter](../cheatsheet)
+
+[Child chapter](cheatsheet)
+
+
 ### Unrelated image
 
 ![Showing rays for different focal points](rays-when-focal-point-moves.gif)
 
+### Unrelated video
+
+<iframe width="560" height="315" sandbox="allow-same-origin allow-scripts" src="https://video.samedi.pm/videos/embed/c06dbd9e-d8c7-4655-aade-51ae95b998c3" frameborder="0" allowfullscreen></iframe>
+
 ---
 
 Morbi suscipit enim tristique hendrerit commodo. Pellentesque quis pulvinar urna. Nulla vel hendrerit neque. Maecenas bibendum sem eget tellus auctor, ac vestibulum ante iaculis. Aenean placerat, nulla vehicula vestibulum suscipit, lacus urna pharetra est, eget pellentesque purus est non tortor. Aenean ac consequat lectus. Praesent varius lacus eu semper tristique. Proin vehicula, velit eu maximus commodo, felis ipsum viverra ex, placerat volutpat risus sem et turpis. Duis faucibus ut eros in facilisis. Duis nulla nisi, interdum quis ornare a, pulvinar ac eros. Aenean non rutrum ante. Suspendisse dui enim, auctor eget enim porttitor, pellentesque pellentesque dolor. Nullam laoreet odio quam, eu laoreet augue venenatis vitae. In nec quam et diam commodo sagittis eget et tellus. Quisque odio sapien, pretium et quam eget, dignissim hendrerit purus. Sed eros sem, semper sit amet tincidunt a, malesuada eget odio.
diff --git a/01.courses/01.optics/04.sources-of-light-physical-ojects/textbook.fr.md b/01.courses/01.optics/04.sources-of-light-physical-ojects/textbook.fr.md
index 91991fac4..d28f1553b 100644
--- a/01.courses/01.optics/04.sources-of-light-physical-ojects/textbook.fr.md
+++ b/01.courses/01.optics/04.sources-of-light-physical-ojects/textbook.fr.md
@@ -3,6 +3,14 @@ title: L'objet physique, source de lumière
 slug: source-de-lumiere-objet-physique
 ---
 
+[Current chapter](.)
+
+[Parent chapter](..)
+
+[Sibling chapter](../cheatsheet)
+
+[Sibling chapter](cheatsheet)
+
 ### L'objet physique, source de lumière
 
 Parmi les cinq sens de l'être humain (vue, ouïe, odorat, goût, toucher),
diff --git a/home/portal.es.md b/home/portal.es.md
new file mode 100644
index 000000000..f9f47cf7b
--- /dev/null
+++ b/home/portal.es.md
@@ -0,0 +1,7 @@
+---
+title: Bienvenida
+slug: bienvenida
+---
+
+# ¡ Bienvenida !
+
diff --git a/home/portal.fr.md b/home/portal.fr.md
index 03ff46515..1b2155062 100644
--- a/home/portal.fr.md
+++ b/home/portal.fr.md
@@ -5,8 +5,8 @@ slug: accueil
 
 # Bienvenue!
 
+M3P2 est un site de formation _en alpha_ qui offre gratuitement des cours.
 
-<!--
-[🇨🇴 ES](/es)
-[🇫🇷 FR](/fr)
--->
\ No newline at end of file
+Vous pouvez vous aussi [contribuer au cours](https://m3p2.ljbac.com/m3p2/courses), comme sur wikipedia.
+
+Ce service à but non-lucratif ne pourrait exister sans [votre support](sponsors).
\ No newline at end of file
diff --git a/test/README.md b/test/README.md
new file mode 100644
index 000000000..7ed09df34
--- /dev/null
+++ b/test/README.md
@@ -0,0 +1,3 @@
+A test page to visually inspect the various markdown features.
+
+We'll perhaps use this as living documentation.
\ No newline at end of file
diff --git a/test/default.md b/test/default.md
new file mode 100644
index 000000000..77b421703
--- /dev/null
+++ b/test/default.md
@@ -0,0 +1,42 @@
+
+# Let's test the features!
+
+0. `*`: *star*
+1. `**`: **globstar**
+2. `_`: _underscore_
+3. `__`: __init__
+5. `~~`: ~~double tilde~~
+5. `~`: tilde
+
+<!-- definition lists -->
+celerity $c$
+: speed of light in a vacuum
+
+<!-- Trailing # are ignored and are sometimes good for readability -->
+### Flowchart ########################################################
+
+```mermaid
+graph LR
+  subgraph M3P2
+    File[File]
+    Website[Website]
+    Pipeline[Pipeline]
+  end
+
+  Teacher((Teacher))
+  Student((Student))
+
+  Student --> |reads| Website
+  Teacher --> |edits| File
+  File --> |triggers| Pipeline
+  Pipeline --> |updates| Website
+```
+
+#### Imagine 💾🐘🐘🐘🐘🐢
+
+```math
+e^{i\tau}=1
+```
+
+> The complex exponential of the circle constant is unity.
+>> $e^{i\tau}=1$
\ No newline at end of file