#container {
    height: 400px;
    width: 600px;
    margin: auto;
    border: 1px solid red;
}
.input-container {
    text-align: center;
    margin-top: 20px;
}
input[type="number"] {
    padding: 10px;
    font-size: 16px;
}
button {
    padding: 10px 20px;
    font-size: 16px;
    cursor: pointer;
}