diff --git a/src/puzzle.sass b/src/puzzle.sass
index 2f29d89..ab0b9f4 100644
--- a/src/puzzle.sass
+++ b/src/puzzle.sass
@@ -17,6 +17,7 @@
 
   &.error
     color: $color-cross
+    background: color.scale($color-cross, $alpha: -90%)
 
   &.complete
     opacity: 0.5