In order to help him complete his task, Berk must make use of the many objects lying around his part of the castle as well as the creatures that emerge from the trap door.

He is also somewhat hindered by Drutt, Berk's pet who loves eating worms, as well as The Thing's impatience which manifests in form of a time limit for each task.

Once Berk has finished taking advantage of a creature's "assistance" he also has to find a way of making sure it goes back down the trap door.

The ghosts hinder the player's progress by attacking Berk, sending him spinning into another room if he does not manage to avoid them.

To promote the release of The Trap Door, Piranha Software partnered with Computer Gamer magazine to run a contest wherein readers submitted recipes for the Thing Upstairs, and 25 winning entrants received a copy of the game.