<style>
.pcA{display: block!important;}
.phA{display: none!important;}
#CKTA>div{position: relative}
.YouTubeVideo{width: 100%;height: 660px;display: block}
@media screen and (max-width:800px) {
.pcA{display: none!important;}
.phA{display: block!important;}
.YouTubeVideo{width: 100%;height: 190px}
}
</style>
<div id="CKTA">
<div>
<img class="pcA" src="https://cdn.shopify.com/s/files/1/0408/5386/4602/files/B001-gray-pc_1.jpg" width="100%">
<img class="phA" src="https://cdn.shopify.com/s/files/1/0408/5386/4602/files/B001-gray-m_1.jpg" width="100%">
</div>
<div>
<img class="pcA" src="https://cdn.shopify.com/s/files/1/0408/5386/4602/files/B001-gray-pc_2.jpg" width="100%">
<img class="phA" src="https://cdn.shopify.com/s/files/1/0408/5386/4602/files/B001-gray-m_2.jpg" width="100%">
</div>
<div>
<img class="pcA" src="https://cdn.shopify.com/s/files/1/0408/5386/4602/files/B001-gray-pc_3.jpg" width="100%">
<img class="phA" src="https://cdn.shopify.com/s/files/1/0408/5386/4602/files/B001-gray-m_3.jpg" width="100%">
</div>