body,
h1,
button,
table {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: "Arial", sans-serif;
    text-align: center;
    background-color: #f9f9f9;
    color: #000;
    margin: 0;
    padding: 20px;
    transition: background-color 0.3s, color 0.3s;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px;
}

h1 {
    margin: 0;
    font-size: 24px;
}

#dark-mode-toggle {
    padding: 10px 20px;
    font-size: 14px;
    background-color: #444;
    color: #fff;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    transition: background-color 0.3s;
}

#dark-mode-toggle:hover {
    background-color: #666;
}

#game-container {
    max-width: 400px;
    margin: 20px auto;
}

#info-container {
    margin-bottom: 10px;
    font-size: 18px;
    font-weight: bold;
}

#sudoku-grid {
    border-collapse: collapse;
    margin: 0 auto;
    border: 3px solid #ccc;
}

#sudoku-grid td {
    width: 40px;
    height: 40px;
    border: 1px solid #ccc;
    text-align: center;
    vertical-align: middle;
    position: relative;
}

#sudoku-grid td:nth-child(3n) {
    border-right: 3px solid #ccc;
}

#sudoku-grid tr:nth-child(3n) td {
    border-bottom: 3px solid #ccc;
}

#sudoku-grid td input {
    width: 100%;
    height: 100%;
    border: none;
    text-align: center;
    font-size: 18px;
    outline: none;
    background: transparent;
    color: gray;
}

#sudoku-grid td input:disabled {
    color: #333;
}

#sudoku-grid td input:focus {
    border: 1px solid #007bff;
}

button {
    margin: 5px;
    padding: 10px 20px;
    font-size: 16px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    background-color: #007bff;
    color: #fff;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #0056b3;
}

#number-buttons {
    display: grid;
    grid-template-columns: repeat(3, 40px);
    grid-gap: 10px;
    justify-content: center;
    margin: 10px 0;
}

#number-buttons button {
    width: 40px;
    height: 40px;
    font-size: 16px;
    border-radius: 4px;
}

body.dark-mode {
    background-color: #121212;
    color: #fff;
}

body.dark-mode #sudoku-grid td input:disabled {
    color: white;
}

body.dark-mode #sudoku-grid td input {
    color: #ccc;
}

body.dark-mode button {
    background-color: #444;
}

body.dark-mode button:hover {
    background-color: #666;
}