public int findHoleNum(){
		int holes = 0;
		for(int col = 0; col<board.getWidth(); col++){
			int lowestRowFilled = 20;
			for(int row = board.getLength()-1; row>=0; row--){
				if(board.getValue(row, col)!=0){
					if(row<lowestRowFilled){
						lowestRowFilled = row;
					}
				}
			}
			for(int row = board.getLength()-1; row>lowestRowFilled; row--){
				if(board.getValue(row, col)==0){
					holes ++;
				}
			}
		}
		return holes;
	}