Doors and keys are among the most important parts of the Phantom Mansion games. There are four types of keys, and four types of doors to match them. Each represents a shape, a circle, a square, a triangle and a cross. To unlock a door, you must have the matching key, for example, a circle door is unlocked by a circle key. Doors and keys are first seen in level 1 of the Red Chamber, "Easy as 1 2 3".