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CSS

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HTML 

              
                <div class="grid-row reverse video-gallery">
 <input type="radio" value="1" name="video-list" id="video-1" checked="checked" /><label for="video-1">Option 1</label>
 <input type="radio" value="2" name="video-list" id="video-2" /><label for="video-2">Option 2</label>
 <input type="radio" value="3" name="video-list" id="video-3" /><label for="video-3">Option 3</label>
 <input type="radio" value="4" name="video-list" id="video-4" /><label for="video-4">Option 4</label>
 <input type="radio" value="5" name="video-list" id="video-5" /><label for="video-5">Option 5</label>
 <input type="radio" value="6" name="video-list" id="video-6" /><label for="video-6">Option 6</label>
 <!-- videos -->
 <div class="video video-1">
  <iframe width="560" height="315" src="https://www.youtube.com/embed/ROqDTIxRX0Y" frameborder="0" allowfullscreen></iframe>
 </div>

 <div class="video video-2">
  <iframe width="560" height="315" src="https://www.youtube.com/embed/9iGoDNlKY-g" frameborder="0" allowfullscreen></iframe>
 </div>

 <div class="video video-3">
  <iframe width="560" height="315" src="https://www.youtube.com/embed/l70UhhNalqA" frameborder="0" allowfullscreen></iframe>
 </div>

 <div class="video video-4">
  <iframe width="560" height="315" src="https://www.youtube.com/embed/XDrB5c4-c9Y" frameborder="0" allowfullscreen></iframe>
 </div>

 <div class="video video-5">
  <iframe width="560" height="315" src="https://www.youtube.com/embed/UXP307MGQzs" frameborder="0" allowfullscreen></iframe>
 </div>

 <div class="video video-6">
  <iframe width="560" height="315" src="https://www.youtube.com/embed/0kY0Q5hdjDI" frameborder="0" allowfullscreen></iframe>
 </div>
 <!-- videos -->
</div>
!

CSS 

              
                *
	box-sizing: border-box

html
	height: 100%
	overflow: hidden
	width: 100%

body
	font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif
	font-size: 16px
	height: auto
	line-height: 1
	overflow-x: hidden
	padding: 2rem
	width: 100%

//everything above here is just for pretties

.video
	position: relative
	padding-top: 4.1%
	padding-bottom: 51.95%
	height: 0
	iframe
		position: absolute
		top: 0
		left: 0
		height: 100%
		width: 100%
		min-height: 0

.video-gallery
	margin-top: 3em
	position: relative
	width: 100%
	.video
		animation: 1200ms fadeOut ease
		animation-fill-mode: both
		//display: none
		grid-column-start: 1
		grid-row-start: 1
		grid-row-end: 7
		//height: 0
		max-height: 19.5em
		opacity: 0
		transition: all 300ms ease
	input[type="radio"]
		font-size: 0
		height: 0
		opacity: 0
		padding: 0
		position: fixed
		width: 0
	input
		grid-column-start: 1
		grid-row-start: 1
	label
		color: #000000
		font-size: 1.25em
		font-weight: 400 
		grid-column-start: 2
		margin: 0 !important
		padding: 1rem 0 1rem 3rem
		position: relative
		border-bottom: 1px solid #CCCCCC
		&:last-of-type
			border: 0 none
	input[type="radio"]:checked+label
		color: #E41F35 !important
		&:before
			content: "▶"
			left: 0
			top: 12px
			position: absolute





.grid-row
	display: block
	height: 56vw
	max-height: 19.5em
	position: relative
	label
		left: calc(50% + 16px)
		position: relative
		width: calc(50% - 16px)
	.video
		padding: 0
		position: absolute
		top: 0
		width: 0
	&:after
		content: ""
		clear: both
		display: table

#video-1:checked ~ .video-1, #video-2:checked ~ .video-2, #video-3:checked ~ .video-3, #video-4:checked ~ .video-4, #video-5:checked ~ .video-5, #video-6:checked ~ .video-6
	animation: 1200ms fadeIn ease
	animation-fill-mode: both
	//display: block
	//height: 56vw
	opacity: 1
	width: 50%




@keyframes fadeOut
	0%
		display: block
		height: 56vw
		opacity: 1
		width: 50%
	25%
		display: block
		height: 56vw
		opacity: 1
		width: 50%
	49%
		display: block
		height: 56vw
		opacity: 0
		width: 50%
	50%
		display: none
		height: 0
		opacity: 0
		width: 0

@keyframes fadeIn
	0%
		opacity: 0
		width: 0
	49%
		display: none
		height: 0
		opacity: 0
		width: 0
	50%
		display: block
		height: 56vw
		opacity: 0
		width: 50%
	100%
		display: block
		height: 56vw
		opacity: 1
		width: 50%





@supports(display: grid)
	.grid-row
		align-items: start
		display: grid
		grid-column-gap: 16px
		grid-row-gap: 0
		grid-template-columns: 1fr 1fr
		grid-template-rows: 1fr 1fr 1fr 1fr 1fr 1fr
		label
			left: auto
			width: 100%
		.video
			position: relative
			width: 100%
		#video-1:checked ~ .video-1, #video-2:checked ~ .video-2, #video-3:checked ~ .video-3, #video-4:checked ~ .video-4, #video-5:checked ~ .video-5, #video-6:checked ~ .video-6
		width: 100%
	@keyframes fadeOut
		0%
			display: block
			height: 56vw
			opacity: 1
			width: 100%
		25%
			display: block
			height: 56vw
			opacity: 1
			width: 100%
		49%
			display: block
			height: 56vw
			opacity: 0
			width: 100%
		50%
			display: none
			height: 0
			opacity: 0
			width: 0

	@keyframes fadeIn
		0%
			opacity: 0
			width: 0
		49%
			display: none
			height: 0
			opacity: 0
			width: 0
		50%
			display: block
			height: 56vw
			opacity: 0
			width: 100%
		100%
			display: block
			height: 56vw
			opacity: 1
			width: 100%





@media (max-width: 767px)
	.video-gallery
		display: flex
		flex-direction: column
		height: auto
		max-height: none
		label
			left: auto
			order: 2
			width: 100%
		.video
			order: 1
			padding-top: 4.1%
			padding-bottom: 51.95%
			position: relative
			top: auto
			width: 100%

	#video-1:checked ~ .video-1, #video-2:checked ~ .video-2, #video-3:checked ~ .video-3, #video-4:checked ~ .video-4, #video-5:checked ~ .video-5, #video-6:checked ~ .video-6
		width: 100%

	@keyframes fadeOut
		0%
			display: block
			height: 56vw
			opacity: 1
		25%
			display: block
			height: 56vw
			opacity: 1
		49%
			display: block
			height: 56vw
			opacity: 0
		50%
			display: none
			height: 0
			opacity: 0

	@keyframes fadeIn
		0%
			opacity: 0
		49%
			display: none
			height: 0
			opacity: 0
		50%
			display: block
			height: 56vw
			opacity: 0
		100%
			display: block
			height: 56vw
			opacity: 1
!

JS 

              
                //What are you looking here for?
!
999px

Console