Double Door! is the fourth level in Doorhaven. This level introduces consecutive doors, requiring the player to carry multiple keys at once.
One major principle in these puzzles is comparing the number of keys with the number of doors. For example: Here there are 8 doors, but only 7 keys! Oh no! I hope this one's solvable...
Opening the bottom green door leaves the player unable to progress further, so the bottom white door must be opened instead. The two white keys are needed to get the two orange keys to get to the goal, so the bottom green key must be used to unlock the green door to the two white keys.
Pick up the green key.
Pick up the white key and open the white door.
Open the top green door and pick up the 2 white keys.
Open the two white doors and pick up the 2 orange keys.
Open the two orange doors and touch the goal.