diff --git a/lib/main.html b/lib/main.html
index 24accf36..830d3b48 100644
--- a/lib/main.html
+++ b/lib/main.html
@@ -57,6 +57,10 @@
opacity: 1 !important;
pointer-events: auto !important;
}
+ .CodeMirror-ruler {
+ border-left-color: rgba(142, 142, 142, 0.5);
+ mix-blend-mode: difference;
+ }