CubeSquared

Easiest way might be to just create the text in a Word / Pages document, strike it through, then copy'n'paste it. Works for me!

Add this to your site, under Settings - Advanced - Code Injection, then scroll down to the Lock Screen section, add this code. The sections in red will need changing to suit whatever you're counting down to and you can play around with fonts, colours, etc.

<div class="container">
  <h1 id="headline">Countdown to my whatever:</h1>
  <div id="countdown">
    <ul>
      <li><span id="days"></span>days</li>
      <li><span id="hours"></span>Hours</li>
      <li><span id="minutes"></span>Minutes</li>
      <li><span id="seconds"></span>Seconds</li>
    </ul>
  </div>
  <div class="message">
    <div id="content">
      <span class="emoji">🥳</span>
      <span class="emoji">🎉</span>
      <span class="emoji">🎂</span>
    </div>
  </div>
</div>
<style>
/* general styling */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

.sqs-slide-wrapper[data-slide-type="lock-screen"] .sqs-slide {
  height: 100%;
  margin: 0;
}

.sqs-slide-wrapper[data-slide-type="lock-screen"] .sqs-slide {
  align-items: center;
  background-color: #ffd54f;
  display: flex;
  font-family: -apple-system, 
    BlinkMacSystemFont, 
    "Segoe UI", 
    Roboto, 
    Oxygen-Sans, 
    Ubuntu, 
    Cantarell, 
    "Helvetica Neue", 
    sans-serif;
}

.container {
  color: #333;
  margin: 0 auto;
  text-align: center;
}

h1 {
  font-weight: normal;
  letter-spacing: .125rem;
  text-transform: uppercase;
}

li {
  display: inline-block;
  font-size: 1.5em;
  list-style-type: none;
  padding: 1em;
  text-transform: uppercase;
}

li span {
  display: block;
  font-size: 4.5rem;
  margin-bottom: 2rem;
}

.message {
  font-size: 4rem;
}

#content {
  display: none;
  padding: 1rem;
}

.emoji {
  padding: 0 .25rem;
}

@media all and (max-width: 768px) {
  h1 {
    font-size: 1.5rem;
  }
  
  li {
    font-size: 1.125rem;
    padding: .75rem;
  }
  
  li span {
    font-size: 3.375rem;
  }
}
</style>
<script>
(function () {
  const second = 1000,
        minute = second * 60,
        hour = minute * 60,
        day = hour * 24;

  let birthday = "Dec 31, 2020 00:00:00",
      countDown = new Date(birthday).getTime(),
      x = setInterval(function() {    

        let now = new Date().getTime(),
            distance = countDown - now;

        document.getElementById("days").innerText = Math.floor(distance / (day)),
          document.getElementById("hours").innerText = Math.floor((distance % (day)) / (hour)),
          document.getElementById("minutes").innerText = Math.floor((distance % (hour)) / (minute)),
          document.getElementById("seconds").innerText = Math.floor((distance % (minute)) / second);

        //do something later when date is reached
        if (distance < 0) {
          let headline = document.getElementById("headline"),
              countdown = document.getElementById("countdown"),
              content = document.getElementById("content");

          headline.innerText = "It's my birthday!";
          countdown.style.display = "none";
          content.style.display = "block";

          clearInterval(x);
        }
        //seconds
      }, 0)
  }());
</script>

Hope this helps! Good luck. (www.twitter.com/cubesqddigital)

Again, thank you so much for taking the time to respond.

@PJ22 This is great thank you. May I ask, how do you make the text repeat from right to left (rather than bounce from side to side? Also, how could you change the font of the scrolling text? Thanks in advance.