How can I make this codepen snippet responsive?

I'm currently making a basic site with my social media links and I was able to use "vw" to get my text to be responsive and change based on your screen size. However, I'm using this and can't figure out how to make it change based on my screen size so that it will look normal on mobile and smaller resolutions. How can I do that?

Code (CSS):

body {
  margin:0;
  padding:0;
  background: #ebebeb;
}
ul {
  position:absolute;
  top:50%;
  left:50%;
  transform:translate(-50%,-50%);
  margin:0;
  padding:0;
  display:flex;
}
ul li {
  list-style:none;
}
ul li a {
  display:block;
  position:relative;
  width:100px;
  height:100px;
  line-height:100px;
  font-size:40px;
  text-align:center;
  text-decoration:none;
  color:#404040;
  margin: 0 30px;
  transition:.5s;
}
ul li a span {
  position:absolute;
  transition: transform .5s;
}
ul li a span:nth-child(1),
ul li a span:nth-child(3){
  width:100%;
  height:3px;
  background:#404040;
}
ul li a span:nth-child(1) {
  top:0;
  left:0;
  transform-origin: right;
}
ul li a:hover span:nth-child(1) {
  transform: scaleX(0);
  transform-origin: left;
  transition:transform .5s;
}

ul li a span:nth-child(3) {
  bottom:0;
  left:0;
  transform-origin: left;
}
ul li a:hover span:nth-child(3) {
  transform: scaleX(0);
  transform-origin: right;
  transition:transform .5s;
}

ul li a span:nth-child(2),
ul li a span:nth-child(4){
  width:3px;
  height:100%;
  background:#404040;
}
ul li a span:nth-child(2) {
  top:0;
  left:0;
  transform:scale(0);
  transform-origin: bottom;
}
ul li a:hover span:nth-child(2) {
  transform: scale(1);
  transform-origin: top;
  transition:transform .5s;
}
ul li a span:nth-child(4) {
  top:0;
  right:0;
  transform:scale(0);
  transform-origin: top;
}
ul li a:hover span:nth-child(4) {
  transform: scale(1);
  transform-origin: bottom;
  transition:transform .5s;
}

.facebook:hover {
  color: #3b5998;
}
.facebook:hover span { 
  background: #3b5998;
}
.twitter:hover {
  color: #1da1f2;
}
.twitter:hover span { 
  background: #1da1f2;
}
.instagram:hover {
  color: #c32aa3;
}
.instagram:hover span { 
  background: #c32aa3;
}
.google:hover {
  color: #dd4b39;
}
.google:hover span { 
  background: #dd4b39;
}
ul li a .twitter {
  color: #1da1f2;
}
ul li a:hover:nth-child(3) {
  color: #c32aa3;
}
ul li a:hover:nth-child(4) {
  color: #dd4b39;
}