I worked in a company that was making games like this. Copy/past the old game, remove assets and start from there. There was a hierarchy of ancestors, siblings

I worked in a company that was making games like this. Copy/past the old game, remove assets and start from there. There was a hierarchy of ancestors, siblings and descendants. So, when a bug is discovered in a game, it was important to trace back its lineage to fix all relatives affected by it. Finally my job was to convert all common code into a library so we could have versioned releases and be able to fix bugs just by upgrading the library version. The copy/past was fast for the very few first games, afterwards was a pain in the ass. When I joined the situation was dire. But , it was an interesting study in evolution, thou.