style.css

body{
    margin: 0px;
    padding: 0px;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #031321;
    font-family: consolas;
}

a{
    position: relative;
    display: inline-block;
    padding: 15px 30px;
    color: #2196f3;
    text-transform: uppercase;
    letter-spacing: 4px;
    text-decoration: none;
    font-size: 24px;
    overflow: hidden;
    transition: 0.2s;
}

a:hover{
    color:#255784;
    background: #2196f3;
    box-shadow: 0 0 10px #2196f3,0 0 40px #2196f3,0 0 80px #2196f3;
    transition-delay: 1s;
    
}

a span{
    position: absolute;
    display: block;
}

a span:nth-child(1){
    top: 0;
    left:-100%;
    width: 100%;
    height: 2px;
    background: linear-gradient(90deg,transparent,#2196f3);
}

a:hover span:nth-child(1){
    left:100%;
    transition: 1s;
}
a span:nth-child(3){
    bottom: 0;
    right:-100%;
    width: 100%;
    height: 2px;
    background: linear-gradient(270deg,transparent,#2196f3);
}

a:hover span:nth-child(3){
    right:100%;
    transition: 1s;
    transition-delay: 0.5s;
}

a span:nth-child(2){
    top: -100%;
    right:0;
    width: 2px;
    height: 100%;
    background: linear-gradient(180deg,transparent,#2196f3);
}

a:hover span:nth-child(2){
    top:100%;
    transition: 1s;
    transition-delay: 0.25s;
}
a span:nth-child(4){
    bottom: -100%;
    left:0;
    width: 2px;
    height: 100%;
    background: linear-gradient(360deg,transparent,#2196f3);
}

a:hover span:nth-child(4){
    bottom:100%;
    transition: 1s;
    transition-delay: 0.75s;
}