.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), #fff);
    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), #fff);
    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), #fff);
    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), #fff);
    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;
    }
}