title: Check if at least one checkbox is checked using HTML5 only
body: <p>I'm making a form using HTML5 validation features.</p>
  
  <p>Example:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  &lt;head&gt;
      &lt;meta charset="utf-8"&gt;
      &lt;title&gt;Form Test&lt;/title&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;form id="form1" method="post" action=""&gt;
          &lt;label&gt;&lt;input type="checkbox" name="color1" value="1" required /&gt;Green&lt;/label&gt;&lt;br /&gt;
          &lt;label&gt;&lt;input type="checkbox" name="color2" value="2" required /&gt;Red&lt;/label&gt;&lt;br /&gt;
          &lt;label&gt;&lt;input type="checkbox" name="color3" value="3" required /&gt;Yellow&lt;/label&gt;&lt;br /&gt;
          &lt;label&gt;&lt;input type="checkbox" name="color4" value="4" required /&gt;Blue&lt;/label&gt;&lt;br /&gt;
          &lt;input type="submit" /&gt;&lt;input type="reset" /&gt;
      &lt;/form&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>I need it to validate if at least one checkbox is checked.</p>
  
  <p><strong>"Must have at least one checkbox checked."</strong></p>
  
  <p>I found answer here:<br />
  <a href="https://stackoverflow.com/questions/2684434/jquery-check-if-at-least-one-checkbox-is-checked">Jquery - check if at least one checkbox is checked</a><br />
  <a href="https://stackoverflow.com/questions/8369904/check-if-at-least-one-checkbox-is-checked-using-jquery">Check if at least one checkbox is checked using jQuery</a><br />
  <a href="https://stackoverflow.com/questions/11787665/making-sure-at-least-one-checkbox-is-checked">Making sure at least one checkbox is checked</a><br />
  <a href="https://stackoverflow.com/questions/22557055/submit-form-only-if-at-least-one-checkbox-is-checked">Submit form only if at least one checkbox is checked</a></p>
  
  <p>But using JavaScript, jQuery and etc.</p>
  
  <p>Is possible make using HTML5 only?</p>