public int checkForRows() {
		// scan for completed rows and remove them
		ArrayList<Integer> rowsToBeCleared = new ArrayList<Integer>();
		boolean test = true;
		for(int i = 0; i < 20; ++i){
			for(int j = 0; j < 10; ++j){
				if(screen[i][j].isEmpty())
					test = false;
			} 
			if(test){
				rowsToBeCleared.add(i);
			} else {
				test = true;
			}
		}
		// update score to reflect rows cleared
		removeRows(rowsToBeCleared);
		return rowsToBeCleared.size();
	}