diff --git a/css/theme/irstea.css b/css/theme/irstea.css
index 8d51fce3c07942a0d1aca2e2d0ddea61375737e6..fbf0873499ef217af2f0c5d5416e0c9ed2928419 100644
--- a/css/theme/irstea.css
+++ b/css/theme/irstea.css
@@ -145,7 +145,7 @@ body {
   font-family: monospace;
   line-height: 1.2em;
   word-wrap: break-word;
-  box-shadow: 0px 0px 6px rgba(0, 0, 0, 0.3); }
+  box-shadow: 0px 5px 15px rgba(0, 0, 0, 0.15); }
 
 .reveal code {
   font-family: monospace;