anchor.diff:      // Alt-O tabs hot-key navigation
       // See app/assets/javascripts/cyber-dojo_codemirror.js
       // See app/views/shared/_hotkeys.html.erb
  -    const editor = cd.kata.editor;
       switch ($selectedTab().text()) {
  -    default               : tabs.stdout().click(); break;
  -    case 'stdout'         : tabs.stderr().click(); break;
  -    case 'stderr'         : tabs.status().click(); break;
  -    case 'status'         : $filenameTab().click(); break;
  -    case $replTab().text(): $filenameTab().click(); break;
  +    default                : tabs.stdout().click(); break;
  +    case 'stdout'          : tabs.stderr().click(); break;
  +    case 'stderr'          : tabs.status().click(); break;
  +    case 'status'          : tabs.filename().click(); break;
  +    case tabs.repl().text(): tabs.filename().click(); break;
       }
     };
   
  -  const $replTab     = () => $('#radio_repl'      , $tabs);
  -  const $filenameTab = () => $('#current_filename', $tabs);
  -  tabs.stdout = () => $('#radio_stdout' , $tabs);
  -  tabs.stderr = () => $('#radio_stderr' , $tabs);
  -  tabs.status = () => $('#radio_status' , $tabs);
  +  tabs.repl     = () => $('#radio_repl'      , $tabs);
  +  tabs.filename = () => $('#current_filename', $tabs);
  +  tabs.stdout   = () => $('#radio_stdout' , $tabs);
  +  tabs.stderr   = () => $('#radio_stderr' , $tabs);
  +  tabs.status   = () => $('#radio_status' , $tabs);
   
     //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   
     const $tabs = $('.tab-filenames');
     const $selectedTab = () => $('.selected', $tabs);
  -  const currentFilename = () => $filenameTab().text();
  +  const currentFilename = () => tabs.filename().text();
     const alreadySelected = $tab => $tab.hasClass('selected');
     const select = $tab => {
       $('.tab-filename').removeClass('selected');
  
positive.code:     // By default the [repl] is hidden.
      const inDev = true;
      if (options.repl !== 'on' && !inDev) {
        $replTab().hide();
      }
    };
  
  
negative.code: 'use strict';
  $(() => {
  
    cd.isOutputFile = filename => ['stdout','stderr','status',tabs.repl().text()].includes(filename);
  
    const tabs = cd.kata.tabs;
  
  