From the introduction: Chambers and Rooms is a set of forty individual rooms on a transparent background, which can be copied and pasted into the blank spaces of Dungeons in Blue Geomorphs, giving the gamemaster additional customization options. There are three versions of each room in this set: one with no doors, one with standard doors, and one with secret doors. To make use of this set, you must have access to a digital paint package, Gimp, Paint, Photoshop, or similar, that supports cut and paste with transparency.