*{
    margin: 0;
    padding: 0;
}
.main{
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
}
.box{
    width: 400px;
    height: 80px;
    background-color: white;
    position: relative;
    border-radius: 20px;
}
.box::before,
.box::after{
    content: "";
    position: absolute;
    background: linear-gradient(45deg,#ff0000,#00f0f0,#00ff00,#0000ff,#ff0000,#00f0f0,#00ff00,#0000ff,#f00f0f);
    width: 100%;
    height: 100%;
    transform: scale(1.02);
    z-index: -1;
    background-size: 500%;
    animation: animation 20s linear infinite;
    border-radius: 20px;
}
.box::after{
    filter: blur(20px);
}
@keyframes animation{
    0%{
        background-position: 0 0;
    }
    50%{
        background-position: 300% 0;
    }
    100%{
        background-position: 0 0;
    }
}