.sudoku-container {
    max-width: 650px;
    margin: 0 auto;
    background: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
    border-radius: 20px;
    padding: 25px;
    box-shadow: 0 10px 40px rgba(0,0,0,0.3);
    font-family: 'Segoe UI', Roboto, sans-serif;
}

.sudoku-header {
    text-align: center;
    margin-bottom: 20px;
}

.sudoku-header h2 {
    color: #fff;
    margin: 0 0 5px;
    font-size: 28px;
}

.sudoku-header h2 i {
    color: #ff6b6b;
    margin-right: 10px;
}

.sudoku-header p {
    color: #aaa;
    font-size: 13px;
    margin: 0;
}

/* Controls */
.sudoku-controls {
    background: rgba(255,255,255,0.1);
    border-radius: 15px;
    padding: 15px;
    margin-bottom: 20px;
}

.difficulty-selector {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 8px;
    margin-bottom: 15px;
}

.difficulty-btn {
    padding: 6px 14px;
    border: none;
    border-radius: 20px;
    background: #2c3e50;
    color: white;
    cursor: pointer;
    font-size: 12px;
    font-weight: 600;
    transition: all 0.3s;
}

.difficulty-btn:hover {
    background: #ff6b6b;
    transform: translateY(-2px);
}

.difficulty-btn.active {
    background: #ff6b6b;
    box-shadow: 0 2px 8px rgba(255,107,107,0.4);
}

.action-buttons {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 10px;
}

.action-btn {
    padding: 8px 16px;
    border: none;
    border-radius: 8px;
    background: #0f3460;
    color: white;
    cursor: pointer;
    font-size: 13px;
    transition: all 0.3s;
}

.action-btn:hover {
    background: #ff6b6b;
    transform: translateY(-2px);
}

/* Sudoku Board */
.sudoku-board-wrapper {
    background: #0f3460;
    border-radius: 12px;
    padding: 15px;
    margin-bottom: 20px;
    overflow-x: auto;
}

.sudoku-table {
    margin: 0 auto;
    border-collapse: collapse;
    background: white;
}

.sudoku-cell {
    width: 55px;
    height: 55px;
    text-align: center;
    vertical-align: middle;
    font-size: 24px;
    font-weight: 600;
    border: 1px solid #ddd;
    cursor: pointer;
    transition: all 0.2s;
    color: #1a1a2e;
}

.sudoku-cell.given {
    color: #ff6b6b;
    font-weight: bold;
}

.sudoku-cell.selected {
    background: #fff3cd;
    box-shadow: inset 0 0 0 2px #ff6b6b;
}

.sudoku-cell.invalid {
    color: #dc3545;
    background: #ffe6e6;
}

.sudoku-cell.border-bottom {
    border-bottom: 2px solid #333;
}

.sudoku-cell.border-right {
    border-right: 2px solid #333;
}

.sudoku-cell:hover:not(.given) {
    background: #e8f4f8;
}

/* Status Area */
.sudoku-status {
    background: rgba(255,255,255,0.1);
    border-radius: 15px;
    padding: 15px;
}

.message-area {
    background: #0f3460;
    border-radius: 10px;
    padding: 12px;
    text-align: center;
    color: white;
    font-size: 14px;
    margin-bottom: 15px;
}

.message-area i {
    margin-right: 8px;
}

.number-pad {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 10px;
}

.number-pad button {
    width: 55px;
    height: 55px;
    border: none;
    border-radius: 12px;
    background: #2c3e50;
    color: white;
    font-size: 20px;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.3s;
}

.number-pad button:hover {
    background: #ff6b6b;
    transform: scale(1.05);
}

.number-pad .delete-btn {
    background: #dc3545;
    font-size: 14px;
}

.number-pad .delete-btn:hover {
    background: #c82333;
}

/* Responsive */
@media (max-width: 600px) {
    .sudoku-container {
        padding: 15px;
    }
    
    .sudoku-cell {
        width: 35px;
        height: 35px;
        font-size: 16px;
    }
    
    .difficulty-btn {
        padding: 4px 10px;
        font-size: 10px;
    }
    
    .action-btn {
        padding: 6px 12px;
        font-size: 11px;
    }
    
    .number-pad button {
        width: 45px;
        height: 45px;
        font-size: 16px;
    }
}

@media (max-width: 480px) {
    .sudoku-cell {
        width: 28px;
        height: 28px;
        font-size: 13px;
    }
    
    .action-buttons {
        gap: 6px;
    }
    
    .action-btn {
        padding: 5px 8px;
        font-size: 10px;
    }
}