body {
    font-family: Arial, sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    background-color: #f0f0f0;
    margin: 0;
    padding: 10px;
    min-height: 100vh;
}

h1 {
    font-size: clamp(1.5rem, 4vw, 2rem);
    margin: 10px 0;
}

.controls {
    margin-bottom: 15px;
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    justify-content: center;
    width: 100%;
    max-width: 500px;
}

.difficulty-selector {
    padding: 8px;
    border-radius: 4px;
    border: 1px solid #ccc;
    font-size: clamp(14px, 2vw, 16px);
}
#new-game-btn {
    background-color: #4CAF50;
}

#check-btn {
    background-color: #2196F3;
}

#hint-btn {
    background-color: #FF9800;
}
button {
    padding: 8px 16px;
    border: none;
    border-radius: 4px;
    background-color: #4CAF50;
    color: white;
    cursor: pointer;
    transition: background-color 0.3s;
    font-size: clamp(14px, 2vw, 16px);
    white-space: nowrap;
}

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

.sudoku-board {
    display: inline-block;
    background-color: white;
    max-width: 100%;
    box-sizing: border-box;
    padding: 0;
    border: 2px solid #333;
}

.sudoku-row {
    display: flex;
    margin: 0;
}

.sudoku-cell {
    width: clamp(30px, 10.5vw, 40px);
    height: clamp(30px, 10.5vw, 40px);
    border-right: 1px solid #ddd;
    border-bottom: 1px solid #ddd;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: clamp(16px, 5vw, 20px);
    cursor: pointer;
    transition: all 0.2s;
    box-sizing: border-box;
    margin: 0;
}

/* 3x3宫格的边框 */
.sudoku-cell:nth-child(3n):not(:last-child) {
    border-right: 2px solid #333;
}

.sudoku-row:nth-child(3n):not(:last-child) .sudoku-cell {
    border-bottom: 2px solid #333;
}

/* 最右列和最底行的边框 */
.sudoku-cell:last-child {
    border-right: none;
}

.sudoku-row:last-child .sudoku-cell {
    border-bottom: none;
}


/* 悬停效果 */
.sudoku-cell:not(.fixed):hover {
    background-color: #f5f5f5;
}

.sudoku-cell:nth-child(9) {
    border-right: 1px solid #ccc;
}

.sudoku-row:nth-child(3n) .sudoku-cell {
    border-bottom: 2px solid #333;
}

.sudoku-row:nth-child(9) .sudoku-cell {
    border-bottom: 1px solid #ccc;
}

/* 固定数字和选中状态 */
.sudoku-cell.fixed {
    background-color: #f8f8f8;
    color: #666;
    cursor: not-allowed;
    font-weight: bold;
}

.sudoku-cell.selected {
    background-color: #e3f2fd;
    box-shadow: inset 0 0 0 2px #2196F3;
}

.sudoku-cell.error {
    background-color: #ffebee;
    color: #f44336;
}

.number-pad {
    margin-top: 15px;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 5px;
    width: 100%;
    max-width: 300px;
    padding: 10px;
}

.number-btn {
    padding: clamp(8px, 2vw, 10px);
    font-size: clamp(16px, 4vw, 18px);
    background-color: #2196F3;
    width: 100%;
}

.clear-btn {
    background-color: #f44336;
    grid-column: 1 / -1;
}

@media (max-width: 360px) {
    body {
        padding: 5px;
    }

    .controls {
        flex-direction: column;
        align-items: stretch;
    }

    button {
        width: 100%;
    }
}