index.css

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

section {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color:#001d30;
    animation: changeBg 5s linear infinite;
}

@keyframes changeBg {
    to{
        filter:hue-rotate(360deg)
    }
}

.loader{
    position: absolute;
    width: 150px;
    height: 150px;
    background: linear-gradient(to top, #001d30 40%, #51eeee);
    border-radius: 50%;
    animation: rotate 2s linear infinite;
}

 @keyframes rotate{
     to{
        transform: rotate(360deg);
     }
}

.loader::before{
    content: '';
    position: absolute;
    background: #001d30;
    inset: 20px 20px 0 0;
    border-radius: 50%;
}

.loader::after {
    content: '';
    position: absolute;
    top: 50px;
    right: -8px;
    width: 40px;
    height: 40px;
    background: #51eeee;/*ned to chack wath the different between backgroung to background color*/
    border-radius: 50%;
    box-shadow: 0 0 5px #51eeee,0 0 75px #51eeee,0 0 75px#51eeee;
}