diff --git a/static/css/cours.css b/static/css/cours.css
index 59cb08f..4d05a94 100644
--- a/static/css/cours.css
+++ b/static/css/cours.css
@@ -1,5 +1,13 @@
 @import "markdown.css";
 
+:root {
+  --max-width: 900px;
+}
+
+main {
+  max-width: var(--max-width);
+}
+
 /* Filetree */
 aside {
   float: left;