.demo__menu {
    list-style: none;
    margin: 3rem;
    position: relative;

    &::after {
        background-color: red;
        clip-path: circle(1rem);
        content: '';
        height: 2rem;
        position: absolute;
        position-anchor: --thumb;
        right: calc(anchor(left) + 1rem);
        transition: top 0.5s ease;
        top: calc(anchor(top) + 1rem);
        width: 2rem;
    }

    & .demo__menu__item {
        border: 1px solid lightblue;
        cursor: pointer;
        margin: 0.25rem 0;
        padding: 1rem;
        user-select: none;

        &:first-child {
            anchor-name: --thumb;
        }

        &:hover {
            anchor-name: --thumb;
            border: 1px solid blue;
        }
    }
}