* {
    margin: 0;
    padding: 0;
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
}

body {
    height: 100vh;
    background: #333;
}

body,
.container {
    display: flex;
    justify-content: center;
    align-items: center;
}

.container {
    position: relative;
    width: 300px;
    height: 400px;
    overflow: hidden;
}

.container,
.container::after {
    background: #222;
    border-radius: 10px;
}

.container .wrap {
    font-size: 18em;
    color: #fff;
    z-index: 3;
}

.container::before,
.container::after {
    content: '';
    position: absolute;
}

.container::before {
    width: 200px;
    height: 500px;
    background: linear-gradient(deepskyblue, deeppink);
    z-index: 1;
    animation: spin 3s linear infinite;
}

.container::after {
    inset: 4px;
    z-index: 2;
}

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
}