Solve This Puzzle Before Opening The Door
This is one door chain not to be taken lightly. When installed on your door, it ensures you have a clear state of mind before you let the person on the other side of the door into your home. All you need is to solve it first!
The Defendius by Art Lebedev Studios, makers of the famous Optimus Maximus keyboard is a door-chain with a maze built into it. Unless you get the end of the chain off the maze, you won’t be able to fully open the door.
While it’s good for waking your brain up before opening the door to strangers, it’s really dangerous when emergencies strike.