#keypad, .keypad-container {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
}

#keypad button, .keypad-container > button {
    margin: 5px;
    padding: 10px;
    font-size: 20px;
    width: 60px;
    height: 60px;
    border: 1px solid #ccc;
    border-radius: 5px;
    background-color: #4e4e4e;
    color: #fff;
}

#keypad button:hover, .keypad-container > button:hover {
    background-color: #727372;
}