Well, if you ever get stuck, you do have hint coins to help you out. I thought I would be bad at those type of puzzles at first, but I quickly found the game to be really fun and don't consider them to be too difficult, aside from some select puzzles, and that's mostly the optional ones.
There are currently five games in the series. The fourth one was just released in the US. The stories are mostly independent of one another, so you don't need to play them all to understand them, but there are numerous cameos and references to previous games, so it's definitely worth playing them all to enjoy the little stuff like that. Not to mention they're all great games anyway.
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Okay, I rolled a 14. What's that mean? Hsu
That you're a cheater. This is a 12-sided die. Chan