adjust background for code highlighting
diff --git a/content/resources/css/arduino-light.css b/content/resources/css/arduino-light.css
index d34c443..a4fe42e 100644
--- a/content/resources/css/arduino-light.css
+++ b/content/resources/css/arduino-light.css
@@ -9,7 +9,7 @@
 */
 
 .hljs {
-  background: #f5f5f5;
+  background: #f7f7f9;
   color: #434f54;
 }