.container {
    display: flex;
    flex-wrap: wrap;
    background-color:aquamarine;
    width: 50vw;
    margin-left: 25vw;
    margin-right: 25vw;
    justify-content: center;
    align-items: center;
    padding: 10px;
}

#number, #generate, #copy {
    width: 100%;
    text-align: center;
    font-weight: bold;
}