Every Mystery Box has the potential to reward you with a Star Coin (most require you to kill an enemy or two first).
If I keep meeting people through Street Pass, or doing whatever else spawns Mystery Boxes on the World Map, can I essentially farm Star Coins this way?
I want to make sure I have as many Star Coins as possible so that I can use them to unlock things as the game progresses.
You can farm up to 999 star coins.
Purple boxes respawn on their own every day or so, but you might get a box you've already cleared.
I think the better option for getting star coins are the levels themselves. You can get up to 285 coins from the 16 worlds and special worlds, and you need 290 coins to unlock the final castle, so the minimum number of purple boxes you'll need to clear is 5.
