.rainbow-wave {
    font-weight: 700;
    font-size: 3.6rem; /* adjust as needed */
    display: inline-block;
    background: linear-gradient(
        90deg,
        red,
        orange,
        yellow,
        lime,
        cyan,
        blue,
        violet,
        red
    );
    background-size: 600%;
    -webkit-background-clip: text;
    color: transparent;

    animation: rainbowSine 9s linear infinite;
}

@keyframes rainbowSine {
    0%   { background-position:   0% 50%; }
    5%   { background-position:  31% 50%; }
    10%  { background-position:  59% 50%; }
    15%  { background-position:  81% 50%; }
    20%  { background-position:  95% 50%; }
    25%  { background-position: 100% 50%; }
    30%  { background-position:  95% 50%; }
    35%  { background-position:  81% 50%; }
    40%  { background-position:  59% 50%; }
    45%  { background-position:  31% 50%; }
    50%  { background-position:   0% 50%; }
    55%  { background-position:  31% 50%; }
    60%  { background-position:  59% 50%; }
    65%  { background-position:  81% 50%; }
    70%  { background-position:  95% 50%; }
    75%  { background-position: 100% 50%; }
    80%  { background-position:  95% 50%; }
    85%  { background-position:  81% 50%; }
    90%  { background-position:  59% 50%; }
    95%  { background-position:  31% 50%; }
    100% { background-position:   0% 50%; }
}

.header{
   background-image: url(https://www.alikonweb.it/images/banners/blue-clouds-day-fluffy-53594.webp);
  background-size: cover;
  background-repeat: no-repeat;
  background-attach: fixed;
  animation: animate-bg 50s infinite linear;
}

@keyframes animate-bg {
  from { background-size: 100%; background-position: 0% 0%; }
  50% { background-size: 120%; background-position: 0% 20% }
  to { background-size: 100%; background-position: 0% 0%; }
}