d_to

d_to is a direction property given to rooms. When a player types, “GO DOWN”, DoGo checks that value to see if there is another room in that direction.

room twistypassage "A Maze of Twisty Passage"
{
    long_desc
        "You are in a maze of twisty passage. There is one exit going down."
    d_to twistypassage2
}