.main-wrapper {
    position: relative;
    z-index: 9;
    overflow: hidden;

    min-height: 100vh;
    background: #232323;
    display: flex;
    align-items: center;
}
.star {
    position: absolute;
    top: -20px;
    color: #fff;
    animation: animate 5s linear forwards;
    /* you can set infinite too */
}
@keyframes animate {
    0% {
        transform: translateY(0) rotate(0deg);
        opacity: 1;
    }
    80% {
        opacity: 1;
    }
    100% {
        transform: translateY(100vh) rotate(360deg);
        opacity: 0;
    }
}
@media screen and (max-width: 600px) {
    .star {
        font-size: 8px;
    }
}