display the 'add password' button only when the input field isn't empty

assets/main.css

@@ -137,6 +137,7 @@ body {
   width: 96%;
 }
 
+pre,
 input,
 select,
 textarea,
@@ -145,6 +146,11 @@ button {
   margin: 0;
 }
 
+pre {
+  font-weight: 600;
+  display: inline-block;
+}
+
 a {
   text-decoration: none;
 }
@@ -809,7 +815,7 @@ tbody {
   padding: 10px 0;
 }
 
-#unlock-input {
+.unlock-input {
   flex: 1;
   height: 46px;
   border: 1px solid #0297f8;
@@ -841,6 +847,14 @@ tbody {
   background-color: #0287e8;
 }
 
+.btn-hidden {
+  visibility: hidden;
+}
+
+.input-no-btn {
+  border-radius: 6px;
+}
+
 /*    footer    */
 .footer {
   right: 0;