I had some very similar ideas. This could be tied into some sort of a base management survival game like Rimworld. Start off with some educated people and nice survival tech like solar panels etc., friendly neighbours and ample access to information and so on. Then try to keep things going as time takes its toll on equipment and people and the climate gets shittier and shittier. First all fancy tech starts to get scarce when global supply chains start to fail and foreign imports stop. The internet starts to go down and you have to get your news via radio, then by mail and then as hearsay. At some point the local government goes fash and starts sending raids to you, or maybe it’s a nearby declining military power that rolls in with some rusty tanks. Neighbours start to get desperate as crops fail and savagery spreads. Or maybe it’s you who will be doing the rading and the cannibalism?

If you get far enough in the game that your original population starts to be replaced, you’d better hope that you managed to preserve at least some of their skills and knowledge by writing books and teaching the kids, because rediscovering shit is a whole lot harder.