body {
    margin: 0;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #111;
    font-family: sans-serif;
}

.rainbow-text {
    font-size: 4rem;
    font-weight: bold;
    background: linear-gradient(to right, red, orange, yellow, green, blue, indigo, violet);
    -webkit-background-clip: text;
    background-clip: text; 
    -webkit-text-fill-color: transparent;
    background-size: 400% 400%;
    animation: rainbow-animation 5s ease infinite;
}

@keyframes rainbow-animation {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
}