html{
    box-sizing: border-box;
}

*,*::before, *::after {
    box-sizing: inherit;
}
#ping-pong-table{
    border: 2px solid black;
    width: 700px;
    height: 400px;
    position: relative;
}

#paddle{
    background-color: blue;
    width : 15px;
    height: 70px;
    margin-left: 2px;
    position: absolute;
}
#ball{
    background-color: red;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    position: absolute;

}