Untitled

<!DOCTYPE html>
<html>

  <head>
    <link rel="stylesheet" href="style.css">
    <script src="script.js"></script>
  </head>

  <body>
    <iframe id="main-frame" src="https://faizalluthfi.gitlab.io/notime-countdown-timer-demo"></iframe>
  </body>

</html>

// Code goes here

html,
body,
#main-frame {
  height: 100%;
  width: 100%;
  margin: 0;
  padding: 0;
  border: 0;
}