.manual-body{
    justify-content: space-around;
    width: 1000px;
    margin: 0 auto;
    font-family: "Times New Roman";
}
h1{
    margin-top: 20px;
    font-size: 20px;
    font-weight: bold;
}
p{
    line-height: 30px;
}
.block-introduction{
    font-weight: bold;
}
.height-introduction{
    color: red;
}
.bottom-introduction{
    text-decoration: underline;
}