body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: #000000;
    margin: 0;
    padding: 0;
}

a {
    font-family: Helvetica;
    font-weight: 700;
    color: aliceblue;
    text-decoration: none;
    text-align: center;
}

.block {
    display: flex;
    justify-content: center;
    align-items: center;
    background: linear-gradient(180deg, #000000, #111111);
    position: relative;
    width: 300px;
    padding: 1rem;
}

.glow::before,
glow::after {
    content: "";
    position: absolute;
    left: -5px;
    top: -5px;
    background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8);
    background-size: 300%;
    width: calc(100% + 10px);
    height: calc(100% + 10px);
    z-index: -1;
    animation: animate 20s linear infinite;
}

@keyframes animate {
    0% {
        background-position: 0 0;
    }

    50% {
        background-position: 300% 0;
    }

    100% {
        background-position: 0 0;
    }

}

.glow::before {
    filter: blur(20px);
    opacity: 0;
    transition: opacity .3s ease-in-out, filter .5s ease-in-out;
}

.glow:hover::before {
    opacity: 100;
    transition: opacity .3s ease-in-out, filter .5s ease-in-out;
}