toggle_lock.html

<!DOCTYPE html>
<html>

<head>
  <title>WOW</title>
  <meta charset="utf-8" />
  <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js"></script>
</head>

<body>
  <style>
    button {
      font-size: 4rem;
    }

    button::before {
      content: "\xF0\x9F\x94\x92";
      animation: moon 1s infinite;
    }

    @keyframes moon {
      50% {
        content: ":unlock:"
      }

      100% {
        content: ""
      }
    }
  </style>

  <button>
    Moon Button
  </button>

</body>

</html>