li{
    list-style: none;
}
*{
    margin: 0;
    padding: 0;
}
.app{
    position: relative;
    background-color: royalblue;
}
.hi{
    width: 120px;
    height: 40px;
    margin-left: 20px;
    margin-top: 20px;
    color: #fff;
    font-size: 16px;
    text-align: center;
    line-height: 40px;
    cursor: pointer;
    background-color: saddlebrown;
}