Unset ?show= after submitting

quiz.js

@@ -7,7 +7,7 @@
  * http://creativecommons.org/publicdomain/zero/1.0/. */
 
 "use strict";
-const version = "$Id: quiz.js,v 1.22 2024/01/21 12:38:48 oj14ozun Exp oj14ozun $";
+const version = "$Id: quiz.js,v 1.23 2024/01/21 13:00:54 oj14ozun Exp oj14ozun $";
 
 const js_version  = document.getElementById("js-version");
 js_version.innerText = version;
@@ -219,6 +219,11 @@ function submit() {
     class_list.add("answer");
     class_list.remove("tried");
     action.disabled = false;
+
+    // remove any permalink
+    const url = new URL(window.location);
+    url.search = "";
+    window.history.replaceState({} , document.title, url.toString());
 }
 
 // listen to keys