diff --git a/_static/demo.css b/_static/demo.css
index e14379af..eaa44104 100644
--- a/_static/demo.css
+++ b/_static/demo.css
@@ -17,6 +17,7 @@
     padding: 2px;
     width: 100%;
     min-height: 150px;
+    resize: vertical;
 }
 
 #hlcode {