anchor.diff:          cd.codeMirror.resetTheme();
         }
       },
  -    theme:(value) => { // Note: theme is different to CodeMirror theme.
  +    theme:(value) => {
         if (value === undefined) {
           return getOption('theme');
         } else {
  
positive.code:   const cache = { colour:undefined, theme:undefined, predict:undefined };
  
    cd.settings = {
      colour:(value) => {
        if (value === undefined) {
          return getOption('colour');
  
negative.code:     <div class="info-title">theme</div>
      <input type="radio" id="light" name="theme" value="light">
      <label for="light">light</label><br/>
      <input type="radio" id="dark"  name="theme" value="dark">
      <label for="dark">dark</label>
    </div>
    <div class="info">
      <div class="info-title">colour syntax</div>
      <input type="radio" id="colour-on"  name="colour" value="on">
      <label for="colour-on">on</label><br/>
      <input type="radio" id="colour-off" name="colour" value="off">
      <label for="colour-off">off</label><br/>
    </div>
    <div class="info">
      <div class="info-title">test prediction</div>
      <input type="radio" id="prediction-on"  name="predict" value="on">
      <label for="prediction-on">on</label><br/>
      <input type="radio" id="prediction-off" name="predict" value="off">
      <label for="prediction-off">off</label><br/>
  