/* #bar　水色の背景色を指定 */
#bar {
    background-color: #0bd;
    position: fixed;
    top: 0;
    left: 0;
    height: 10px;
    /* width: 100%; */
}
article {
    max-width: 800px;
    margin: auto;
    padding: 2rem;
    line-height: 1.8;
}
h2 {
    margin: 2rem 0 1rem;
}