.btn-anim{

transition: all .5s;
position: relative;
overflow: hidden !important;
box-shadow: 0px 1px 2px rgba(0,0,0,.2);
}
.btn-anim span{
position: absolute;
display: block;
}
.btn-anim span:nth-child(1){
height: 3px;
width:200px;
top:0px;
left:-200px;
background: linear-gradient(to right, rgba(0,0,0,0), #f00);
border-top-right-radius: 25px;
border-bottom-right-radius: 25px;
animation: span1 2s linear infinite;
animation-delay: 0s;
}

@keyframes span1{
0%{
left:-200px
}
100%{
left:200px;
}
}
.btn-anim span:nth-child(2){
height: 70px;
width: 3px;
top:-70px;
right:0px;
background: linear-gradient(to bottom, rgba(0,0,0,0), #f00);
border-bottom-left-radius: 25px;
border-bottom-right-radius: 25px;
animation: span2 2s linear infinite;
animation-delay: 0s;
}
@keyframes span2{
0%{
top:-70px;
}
100%{
top:70px;
}
}
.btn-anim span:nth-child(3){
height:3px;
width:200px;
right:-200px;
bottom: 0px;
background: linear-gradient(to left, rgba(0,0,0,0), #f00);
border-top-left-radius: 25px;
border-bottom-left-radius: 25px;
animation: span3 2s linear infinite;
animation-delay: 0s;
}
@keyframes span3{
0%{
right:-200px;
}
100%{
right: 200px;
}
}

.btn-anim span:nth-child(4){
height:70px;
width:3px;
bottom:-70px;
left:0px;
background: linear-gradient(to top, rgba(0,0,0,0), #f00);
border-top-right-radius: 25px;
border-top-left-radius: 25px;
animation: span4 2s linear infinite;
animation-delay: 0s;
}
@keyframes span4{
0%{
bottom: -70px;
}
100%{
bottom:70px;
}
}