body {

    display: flex;

    flex-direction: row;

    flex-wrap: wrap;

    margin: 0;

    padding: 0;

    min-height: 100vh;

    outline: 1px solid green;

    background-color: lime;

    align-content: flex-start;

    >a {

        padding: 10px;

        margin: 0 5px;

        order: -1;

        flex-grow: 0;

        border: solid gray;

        border-width: 1px 1px 0 1px;

        &:last-of-type {

            order: -2;

        }

    }

}   

​

section {

    width: 100%;

    background-color: cornsilk;

    display: none;

    border-top: 1px solid grey;

    &:last-of-type {

        display: flex;

    }

}

a {

    font-weight: normal;

    &:last-of-type {

        font-weight: bold;

    }

}

:target {

    display: flex;

    ~section {

        display: none;

    }

    ~a {

        font-weight: normal;

    }

    +a {

        font-weight: bold;

    }

}

​

​