- and that is actually surprising, as I do the same over and over each time I start a new game.
So what is the hook? For me it is the unlock system.

Whenever you start a new game you are reminded about 3 yet unfill 'archivements', and whenever an archivement is filled you unlock something to use in the next game.
Something similar could be used in Factorio outside the Campaign, but I'm not even sure myself if it should.
I guess there are strong feelings against 'unlocks', as it is indeed an artificial way of extending the life of a game, and one of Factorio's strengths is that it can handle the complexity of 100+ hour factories.
Anyway, - I still think it's an idea worth sharing.

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Abour Reus. http://www.reusgame.com/
I love it, but it is a very 'unique' game that not everyone will like, so watch some review before buying it.