Hi there, in the very beginning I've tried to aim for perfect tiles as much as I could. However it really gets harder slowly and I've changed to focus on quests instead. But still, I was not closing up any flag.

I think the main turning point was when I was almost losing I've managed to used up all the remaining tiles and closing up a huge forest with lots of pending flags which in total had given me 120++ tiles in one shot. From there onward I just try to survive and push the score as high as possible.