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... When I've finished all the puzzles, I can either start over, or just see how long I can keep a tribe going.

If I'm playing The Lost Children or The Secret City, I can try for all the collectibles. No matter what, there's always "something" to do!
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My suggestion is that you try to start a new tribe, now that you know more about how to solve the puzzles. I'm sure you'll be pleased to find the game goes much faster the second time around.

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