html-css-javascript-online-editor-compiler

@import url(https://fonts.googleapis.com/css?family=Open+Sans);
body{
    background-color: #000;
    text-align: center;
    min-height: 270px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: "Open Sans";
}
.btn-glow {
    padding: 15px 35px;
    min-width: 250px;
    border-radius: 100px;
    color: #fff;
    background: #141414;
    cursor: pointer;
    position: relative;
    z-index: 0;
    font-size: 16px;
}

.btn-glow:before {
    content: '';
    background: linear-gradient(320deg, #e91e63, #ff5722, #ffeb3b, #b9ff68, #0fac81, #084298, #771afe, #970374, #e91e63);
    position: absolute;
    top: -4px;
    left: -4px;
    background-size: 500%;
    z-index: -1;
    filter: blur(5px);
    width: calc(100% + 8px);
    height: calc(100% + 8px);
    animation: btn-glowing 15s linear infinite;
    opacity: 0;
    transition: opacity .5s ease-in-out;
    border-radius: 100px;
}

.btn-glow:hover:before {
    opacity: 1;
}

.btn-glow:after {
    z-index: -1;
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    background: #141414;
    left: 0;
    top: 0;
    border-radius: 100px;
}

@keyframes btn-glowing {
    0% { background-position: 0 0; }
    50% { background-position: 500% 0; }
    100% { background-position: 0 0; }
}

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