This is an order sensitive combination lock with buttons. The circuit is very small and easy to build in survival. Only 7x3x14!
The combination lock has 6 buttons, but it is possible to make it bigger. Every time you press wrong combination, the lock automatically resets. This makes the lock secure and easy to use. When the lock is open, all the buttons works like a reset button. This makes it easy to close the door from the outside. Just press a random button.

Each button has one RS NOR latch. When all the RS NOR latches are activated, the combination is correct, and the T flip-flop in the circuit activates. The T flip-flop turns off when one of the buttons sends a reset signal.