.videoIntroduction-main-wrapper {
	position: relative;
}

.videoIntroduction-main-wrapper.overlay {
	left: 0;
	z-index: 5;
}

.videoIntroduction-main {
	padding: 0 10% 3.5em 10%;
	position: relative;
}
.content-box{
	background-color: #f9f9f9;
}

#main_video_div{
	margin:3rem auto;
}

.intro-video{
	width: 100%;
	background-color: #222;
	margin:0 auto;
}

.intro-video video{
	width: 100%;
	height: 100%;
	
}
.videos_il {
	float:left;
}

.thumbnail img{
	width: 100%;
}

#videos_div{
	text-align: center;
}

#videos_div h3{
	text-align: left;
}

.video-explanation{
	font-size: 1rem;
}

.video-title-p{
	font-size: 0.8rem;
	line-height: 2rem;
}

.videoIntroduction-main h3:before {
	content: '';
	position: absolute;
	margin-top: .6em;
	left: 0%;
	height: 40px;
	width: 15%;
	border-bottom: 2px solid rgb(182 182 182);
}

.title-box {
	display: inline-block;
	padding: .7em 1.4em;
	background-color: #222;
	margin-bottom: 10px;
	margin-top: 30px;
	color: #fff;
}

.contents-header {
	position: sticky;
	top: 0;
	z-index: 20;
}

.thumbnail {
    margin: 0 auto;
    display: inline-block;
}

.thumbnail-width {
    width: 100%;
    padding:1rem;
}

@media all and (min-width:350px){
	.thumbnail-width {
	    width: 100%;
	}
}
@media all and (min-width:920px){
	.thumbnail-width {
	    width: 50%;
	}
}
@media all and (min-width:1510px){
	.thumbnail-width {
	    width: 33%;
	}
}
@media all and (min-width:1890px){
	.thumbnail-width {
	    width: 24%;
	}
}