.sudoku-board {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    width: clamp(300px, 90vw, 540px);
    height: clamp(300px, 90vw, 540px);
    margin: 1rem auto;
    border: 3px solid #1a1a1a;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
    background-color: #fff;
}

.sudoku-cell {
    width: 100%;
    height: 100%;
    border: 1px solid #e0e0e0;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: clamp(16px, 4vw, 28px);
    font-weight: bold;
    cursor: pointer;
    box-sizing: border-box;
    transition: background-color 0.2s ease-in-out;
    color: #4a4a4a;
}

.sudoku-cell:hover {
    background-color: #f5f5f5;
}

.sudoku-cell.given {
    background-color: #f9f9f9;
    color: #333;
    font-weight: 900;
    cursor: not-allowed;
}

.sudoku-cell.selected {
    background-color: #bbdefb;
    position: relative;
}

.sudoku-cell.selected::after {
    content: '';
    position: absolute;
    top: -2px; left: -2px; right: -2px; bottom: -2px;
    border: 2px solid #2196f3;
    border-radius: 2px;
    pointer-events: none;
}

.sudoku-cell.mistake {
    background-color: #ffebee;
    color: #c62828;
    animation: shake 0.5s;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    10%, 30%, 50%, 70%, 90% { transform: translateX(-5px); }
    20%, 40%, 60%, 80% { transform: translateX(5px); }
}

.sudoku-cell.border-bottom {
    border-bottom: 2px solid #999;
}

.sudoku-cell.border-right {
    border-right: 2px solid #999;
}

.sudoku-controls {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    margin-top: 1rem;
}

.sudoku-info {
    display: flex;
    gap: 1.5rem;
    font-size: 1rem;
    color: #555;
    background-color: #f7f7f7;
    padding: 0.5rem 1rem;
    border-radius: 8px;
}

.sudoku-palette {
    display: flex;
    gap: 0.5rem;
}

.palette-number {
    width: 40px;
    height: 40px;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #fff;
    border: 1px solid #ccc;
    border-radius: 8px;
    font-size: 20px;
    font-weight: bold;
    cursor: pointer;
    transition: background-color 0.2s, transform 0.2s;
}

.palette-number:hover {
    background-color: #e3f2fd;
    transform: translateY(-2px);
}