We store information about the key in the game mode so that we can access it no matter where the player, key, or door is. If the data is in the key, nothing much changes, but I don't think the blueprint will carry over to a new world. If it is in the door, then the code needs to be copied over every time we want to grab the key's data. Keeping it in the game mode blueprint helps minimize necessary code. The hardest part about the key and door excercise was understanding the code. Even having it walked through, I have a hard time visualizing the hoops the code jumps through to get to where it's going. I suppose this knowledge comes with time, but writing down notes might help.