How would you even make a game like that?

So I've been spending a lot of time thinking about how to begin making a game which mimics existence. The first thing I realized is that I would have to take the lazy man approach and try to disguise it as genius.

My main idea so far, or the main design so far, is a blank page with the game title and a button labeled "These things I know to exist". Clicking that button would open up a menu of the items you have created/encountered/discovered. From this menu, I think, you would be able to introduce new instances of existing items into your universe.

I think also in the menu you would have a little sandbox where you could pre-combine items to see how they react and decide if they should be included in your universe. Once created, though, you could not remove them yourself, unless other items in existence conspired to have them removed.

So you would need to create a series of creators and destroyers to keep the balance, with other inanimate (so to speak) objects floating around doing their own thing among all the action.

My big goal is to have a working universe which can live on its own, simulate decision-making and, eventually, interact with other user-created universes. But I'm going to start small.