body {
    margin: 0;
    overflow: scroll;
}

#sample1,#sample2,#sample3,#sample4,#sample5 {
    float:left;
}

#space,#space1,#space2,#space3,#space4,#space5 {
    width: 520px;
    clear:both;
}

#a1,#a2,#a3,#a4,#a5 {
    width: 350px;
    height: 30px;
    background-color:rgb(14, 221, 14);
    margin: 5px auto;
    text-align: center;
    line-height: 30px;
    font-size: 18px;
    font-weight: bold;
    color: #fff;
    user-select: none;
    float:left;
}

#contents {
    font-size: 18px;
    margin: 30px auto;
}

#start {
    width: 350px;
    height: 30px;
    background-color:rgb(14, 221, 14);
    margin: 0px auto;
    text-align: center;
    line-height: 30px;
    font-size: 18px;
    font-weight: bold;
    color: #fff;
    user-select: none;
    float:left;
}