Two of a Kind is the second level of Doorhaven. It presents a situation where the player is likely to run into an unsolvable situation and need to use the undo option.
Description
If you ever find yourself in an unsolvable position in a puzzle, press [Z] to rewind your actions, or [R] to completely restart. You can also press [BSpace] to leave a level and come back to it later. With that said, here's a puzzle you can conceivably fail!
Puzzle Logic
Going straight for the orange key after getting the white key makes the player unable to open the white door to the exit. Instead the player must open the bottom white door first and then use the second white key to get the orange key.
Solution
Pick up the white key.
Open the bottom white door and pick up the other white key.
Open the top white door and pick up the orange key.
Open the orange door and touch the goal.