diff --git a/src/sass/_bootstrap.scss b/src/sass/_bootstrap.scss
index f7c471c..96de592 100644
--- a/src/sass/_bootstrap.scss
+++ b/src/sass/_bootstrap.scss
@@ -76,3 +76,7 @@ input[type=number]::-webkit-outer-spin-button {
   -webkit-appearance: none; 
   margin: 0; 
 }
+
+.invisible {
+    color: rgba(0,0,0,0);
+}
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