<h1>Pure CSS Gradient Background</h1>

@import url('https://fonts.googleapis.com/css2?family=Raleway:wght@200 &display=swap');

body {
    background: linear-gradient(-45deg, #ee7752, #e73c7e, #23a6d5, #23d5ab);
    background-size: 400% 400%;
    animation: gradient 15s ease infinite;
}
h1 {
    display: flex;
    justify-content: center;
    align-items: center;
    margin-top: 20%;
    font-family: 'Raleway', sans-serif;
    text-transform: uppercase;
    color: rgb(43, 38, 38);
    font-size: 1.5em;
}
@keyframes gradient {
    0% {
        background-position: 0 50%;
    }
    50% {
        background-position: 100% 50%;
    }
    100% {
        background-position: 0 50%;
    }
}