diff --git a/index.html b/index.html
index cdfcdc4..68e2107 100644
--- a/index.html
+++ b/index.html
@@ -11,6 +11,10 @@
          --secondary-color: #99b;
      }
 
+     *, *:before, *:after {
+         box-sizing: border-box;
+     }
+
      html, body {
          padding: 0;
          margin: 0;