This game has NPCs that automatically chop wood and mine stone for resources, but don't expect to clear it just with that...

I started playing this game because of the time-limited mission rewards. The game also has hidden missions, which are for upgrading your ship. There are NPCs that automatically chop wood and mine stone to gather resources, but don't think you can complete the hidden missions relying solely on them, because the resources NPCs collect are never enough, and the gathering speed is too slow to complete the hidden missions. Also, NPCs can suddenly get sick and can't work, suddenly die from accidents, or die from overwork due to being too tired. Pirates also attack periodically. The first and second pirate attacks are polite, but after the 3rd or 4th time, an NPC is guaranteed to be killed. **You must diligently watch ads to accumulate various resources (wood, stone, food, gold, gems), and continuously upgrade NPC skills to have any hope of clearing the game. However, 'don't expect to clear the game quickly by watching a lot of ads' because the game mechanics will prevent you from progressing if you haven't met certain thresholds: for example, tents and houses relate to the number of NPCs. Increasing the number of buildings and upgrading them can increase the number of NPCs to a certain extent, but unless you upgrade to a higher-level ship, the number you can build is fixed, and there are also limits to the upgrade levels and the number of NPCs. **Furthermore, NPCs will start dying continuously and rapidly once the game progresses to a certain point, when you feel like you're about to clear it. ***Yet, you absolutely need to watch a large amount of ads continuously to accumulate resources to upgrade your ship*** **I upgraded my ship to level 7 (there were levels 3 and 5 before), and after watching at least 200-300 ads, I was finally able to clear it and get the hidden mission reward. I gave up on Frost Island immediately.