Let's say I'm making a top-down, turn based RPG (or roguelike/roguelite/whatever). So upon first entering a particular level, all the items, monsters, etc., basically all interactable items are set and ready to be interacted with. So, say I pick up some items and kill some monsters (not all of them), and then I exit the level, and go try another one. When I come back to the mentioned level, the items and monsters with which I interacted shouldn't be there anymore. Basically the state of every level is saved every time I exit it and reloaded when I come back again. I do have several ideas on this, but I'm not sure if those would be the way to go, or would those be too demanding resource-wise, or just require massive additional time to set it up properly, but maybe there are more experienced people on this matter, so my question is, what is the best way to do this? Am I missing something easy along the way?