body {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #f4f4f4;
}

#sudokuContainer {
    display: grid;
    grid-template-columns: repeat(9, 50px);
    grid-template-rows: repeat(9, 50px);
    gap: 1px;
    border: 2px solid #333;
}

.cell {
    width: 50px;
    height: 50px;
    line-height: 50px;
    text-align: center;
    font-size: 16px;
    font-weight: bold;
    color: #333;
    background-color: #fff;
    border: 1px solid #ccc;
}

.cell.correct {
    background-color: #aaffaa;
}

.cell.incorrect {
    background-color: #ffaaaa;
}

button {
    margin-top: 10px;
    padding: 10px;
    font-size: 16px;
    background-color: #4caf50;
    color: white;
    border: none;
    cursor: pointer;
}

button:hover {
    background-color: #45a049;
}

#timer {
    margin-top: 10px;
    font-size: 18px;
    font-weight: bold;
}