<div class="shadow">
    <div class="header">
        <h1>Pure CSS Gradient Text & shadow gradient Animation Effect</h1>
    </div>
 </div>
 

/**
 * index.scss
 * - Add any styles you want here!
 */
*{margin: 0;padding: 0;}

body{margin: 0;padding: 0;background: #000}


.shadow{
    position: relative;
    margin: 100px auto 0;
    width: 400px;
    height: 250px;
    background: linear-gradient(0deg, #000, #262626);
    border-radius: 10px;
}

.shadow:before, .shadow:after{
    content: '';
    position: absolute;
    top: -2px;
    left: -2px;
    background: linear-gradient(45deg, #fb0094, #0000ff,#00ff00,#ffff00,#ff0000, #fb0094, #0000ff,#00ff00,#ffff00,#ff0000);
    background-size: 400%;
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    z-index: -1;
    animation: animate 20s linear infinite;
    border-radius: 10px;
}

.shadow:after{
    filter: blur(20px);
}

.header {
    display: flex;
    align-items: center;
    height: 100%;
    width: 90%;
    margin: 0 auto;
}

.header h1{
    font-family: Helvetica Neue, Helvetica, Arial, sans-serif;
    font-size: 2rem;
    font-weight:  100;
    letter-spacing: 2px;
    text-align: center;
    color: #fb0094;
    background-image: -webkit-linear-gradient(92deg, #fb0094, #00ff00, #00ff00);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    -webkit-animation: hue 10s infinite linear;
}

@-webkit-keyframes hue {
    from {
        -webkit-filter: hue-rotate(0deg);
    }
    to {
        -webkit-filter: hue-rotate(-360deg);
    }
}


@keyframes animate {
    0%{
        background-position: 0 0;
    }
    50%{
        background-position: 300% 0;
    }
    100%{
        background-position: 0 0;
    }
}