Types $08-$0B, the red, green, cyan and yellow doors. Asks DOOR_NEEDS_KEY whether the player has the matching key. With one, once the player is in the doorway, it sets both halves' type to $02 -- a plain door -- through SET_BOTH_HALVES and goes through ENTER_ROOM: the door stays an ordinary door for the rest of the game, and the key is kept. Without one it just draws itself shut.