body {
    margin: 0;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(lightyellow, burlywood);
}

.pendulums {
    width: 40em;
    height: 30em;
    font-size: 10px;
    border-top: 0.3em solid cadetblue;
    position: relative;
}

.pendulums span {
    position: absolute;
    width: 0.2em;
    height: calc((var(--n) - 1) * 1em + 15em);
    background-color: cadetblue;
    left: 50%;
    transform-origin: 50% top;
    transform: rotate(25deg);
    animation: swing ease-in-out infinite;
    animation-duration: calc((var(--n) - 1) * 0.02s + 1.5s);
}

@keyframes swing {
    50% {
        transform: rotate(-25deg);
    }
}

.pendulums span::before {
    content: '';
    position: absolute;
    width: 1.5em;
    height: 1.5em;
    background: radial-gradient(
        circle at 70% 35%,
        white,
        darkturquoise 30%,
        steelblue 50%
    );
    border-radius: 50%;
    top: 100%;
    left: -0.75em;
}

.pendulums span::after {
    content: '';
    position: absolute;
    width: 2em;
    height: 0.3em;
    background-color: rgba(0, 0, 0, 0.2);
    top: 120%;
    left: -1em;
    filter: blur(0.4em);
}