.title {
    font-size: 40px;
    font-weight: 700;
    margin: 20px 0 50px 20px;
}
.explanation {
    height: 1000px;
    margin: 100px;
}
.comment {
    margin: 50px 0;
    padding: 30px 20px;
    background: rgb(235, 232, 232);
    line-height: 1.3;
}



#page_top {
    position: fixed;
    bottom: 30px;
    right: 20px;
    display: none;
}
#page_top a {
    background-color: #999;
    color: #fff;
    text-align: center;
    text-decoration: none;
    padding: 20px 20px;
}
#page_top a:hover {
    background-color: #666;
    text-decoration: none;
}