html,body {
    width: 100%;
    height: 100%;
}

body{
    background-color: rgb(233,233,233);
    padding: 10px;
}

.centering{
    display:flex;
    justify-content:center;
    align-items:center;
    height: 100%;
    color: rgba(0, 0, 0, 0.6);
    text-align: center;
}

.centering .main{
    font-size: x-large;
    font-weight: bold;;
}
.centering .sub{
    font-size: medium;
}