@keyframes spin{
    0%{transform: rotate(0deg);}
    25%{transform: rotate(0deg);}
    100%{transform: rotate(359deg);}
}
#con{
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    }
#cool{
    animation: spin 10s infinite;
    padding: 10px;
    background-image: linear-gradient(90deg, #f00, #ff0, #0f0, #0ff, #00f);
}
body{
  background-color: #000;
  color: #fff;
}