Change rhythm indicator to use alt modifier

       }
       return
     }
-    if (ev.ctrlKey && ev.key == '.') {               // C^. toggle rhythm indicator
+    if (ev.altKey && ev.key == '.') {                // A-. toggle rhythm indicator
       if (cookies.get('rhythm') == 'on') {
         document.querySelector('body').style.backgroundImage = 'none'
         cookies.set('rhythm', 'off')