@import url("https://fonts.googleapis.com/css?family=Poppins:200, 300, 400, 500, 600, 700,800, 900&display=swap");
*
{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "Poppins", sans-serif;
}
body
{
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #000;
}
a
{
    position: relative;
    padding: 10px 30px;
    margin: 0 15px;
    background: #21ebff;
    text-decoration: none;
    text-transform: uppercase;
    letter-spacing: 2px;
    font-size: 20px;
    overflow: hidden;
    transition: 0.5s;
    /* -webkit-box-reflect: below 1px linear-gradient(transparent,#003) */
}
a:nth-child(1)
{
    filter: hue-rotate(115deg);
}
a:nth-child(3)
{
    filter: hue-rotate(270deg);
}
a:hover
{
    background: #21ebff;
    color: #111;
    box-shadow: 0 0 50px #21ebff;
    transition-delay: 0.5s;
}
a:before
{
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    width: 10px;
    height: 10px;
    border-top: 2px solid #21ebff;
    border-left: 2px solid #21ebff;
    transition: 0.5s;
}
a:hover:before
{
    width: 100%;
    height: 100%;}
a:after
{
    content: "";
    position: absolute;
    bottom: 0;
    right: 0;
    width: 10px;
    height: 10px;
    border-bottom: 2px solid #21ebff;
    border-right: 2px solid #21ebff;
    transition: 0.5s;
}
a:hover:after
{
    width: 100%;
    height: 100%;}