In this video I build a complete door + key system in Unreal Engine 5 where doors are locked by default and only unlock when you collect the correct key. I start by showing the result with three doors and three keys (bedroom, store room, main room), and how each key only unlocks its own door while the other doors stay locked. This is the same kind of mechanic you’ll see in horror and puzzle games, and the nice part is once you implement it, you can add as many doors and keys as you want. I also explain two ways to handle interaction: the proper scalable interaction system (using my base interactable blueprint), and a quick overlap + “press E” setup for people who just want to get it done. For the actual key logic, I use a Blueprint Interface so the key can tell the character to “collect key,” then the character stores collected keys as a Name array. On the door side, I use a door name (Name) and a locked/unlocked boolean, then call a “use key” interface function on the character to check the array, remove the matching key, unlock the door, and open it with a smooth timeline rotation. Finally, I show how I display UI messages like “you collected bedroom key” and “bedroom door unlocked / door is locked.”