.background-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    overflow: hidden;
}

.rainbow-gradient {
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: linear-gradient(
        217deg, 
        rgba(255, 0, 0, 0.6), 
        rgba(255, 0, 0, 0) 70.71%
    ), linear-gradient(
        127deg, 
        rgba(0, 255, 0, 0.6), 
        rgba(0, 255, 0, 0) 70.71%
    ), linear-gradient(
        336deg, 
        rgba(0, 0, 255, 0.6), 
        rgba(0, 0, 255, 0) 70.71%
    );
    animation: rainbow-rotate 15s linear infinite;
}

@keyframes rainbow-rotate {
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
}