This is an image comparison slider.
Lightning implementation:
<!-- This sets the height of the container. Set value depending on max height of image. -->
<div style=”max-height:980px!important;”>
<!-- .mm makes it responsive and the padding-bottom makes it fill the full image -->
<div class=”mm” style=”padding-bottom:100%;”>
<!-- This is the iframe to the github page. Height is max height -->
<iframe src=”http://pages.registergaurd.com/slider/” width=”100%” height=”980” frameBorder=”0” scrolling=”no”></iframe>
</div>
</div>
See https://github.com/registerguard/tracker/issues/455 for more info.
Code tutorial: Mobile-friendly, responsive scrubber