Responsive absolute positioned elements - responsive-design

Question

I have an image slider but need to have a link on one side. I have currently set the link where I want it on the image but it doesn't scale down when the screen is resized.
How do I get this absolute positioned element to scale down with the screen size and move with the image resizing?
here is a JSFiddle https://jsfiddle.net/s0v6j04a/
<div class="sliders">
<div class="slider"><div id="promo1">
<div id="promo-link">
TEST LINK
</div>
<img src="https://unsplash.imgix.net/photo-1434139240289-56c519f77cb0?fit=crop&fm=jpg&h=700&q=75&w=1050" />
</div>
</div>
</div>
#slider{
position:relative;
}
.div1, .div2 {
min-height: 400px;
background: #D25A1E;
position: relative;
width: calc(50% - 30px);
}
.div1 {
float: left;
background-image: url('https://ununsplash.imgix.net/photo-1433838552652-f9a46b332c40?fit=crop&fm=jpg&q=75&w=1050') !important;
background-repeat: no-repeat;
background-position: center center;
-o-background-size: 100% 100%, auto;
-moz-background-size: 100% 100%, auto;
-webkit-background-size: 100% 100%, auto;
background-size: 100% 100%, auto;
}
.div2 {
float: right;
background-image: url('https://ununsplash.imgix.net/photo-1427805371062-cacdd21273f1?fit=crop&fm=jpg&q=75&w=1050') !important;
background-repeat: no-repeat;
background-position: center center;
-o-background-size: 100% 100%, auto;
-moz-background-size: 100% 100%, auto;
-webkit-background-size: 100% 100%, auto;
background-size: 100% 100%, auto;
}
.div1:after, .div2:before {
content:'';
position: absolute;
top: 0;
width: 0;
height: 0;
}
.div1:after {
left: 100%;
border-top: 400px solid #D25A1E;
border-right: 50px solid transparent;
}
.div2:before {
right: 100%;
border-bottom: 400px solid #D25A1E;
border-left: 50px solid transparent;
}
#promo1{width:100%; position:relative;}
#promo1 img{width:100%;}
#promo-link{
position: absolute;
z-index: 100000;
left: 25%;
top: 50%;
font-size: 30px;
padding: 20px 40px;
border: 2px solid #fff;
}
#promo-link a{
text-decoration:none;
color:#fff;
font-family:"Times New Roman", Times, serif
}