body {
    padding: 0;
    margin: 0;
}

input[type="text"] {
    width: 40px;
    height: 40px;
    text-align: center;
    font-size: 18px;
    margin: 0;
    background-color: #ffffff; 
    color: #000000; 
    padding: 0; 
    box-sizing: border-box;
}

.button-group {
    display: flex;
    justify-content: space-between;
    margin-top: 10px;
}

@media (max-width: 768px) {
    input[type="text"] {
        width: 30px;
        height: 30px;
        font-size: 16px;
    }
    .button-group {
        flex-direction: column;
        gap: 10px;
    }
}

.input-group {
    display: flex;
    gap: 2px;
    flex-wrap: wrap;
    justify-content: center;
}

.container {
    max-width: 700px;
    margin: auto;
    padding: 20px;
}