5 backgrounds and 18 objects in 4 groups. Positions are cells (U, V, level): U and V 0-7, sixteen units a cell from 72; each level twelve units up from the floor.

The room directory: 128 records, one per room, end to end up to OBJECT_TABLE. BUILD_ROOM finds a room by stepping from one record to the next until the number matches; the rooms are numbered on a 16 by 16 grid, as in Knight Lore.

A record is +0 the room number, +1 the count of bytes from +1 to the end of the record, +2 the room's size (bits 6-7, an index into ROOM_SIZES) and its colour: bits 3-5 on the tape, copied into bits 0-2 at the start of every game (RESET_ROOM_COLOURS) because bits 0-2 are the ink in use, which an activated chamber turns white (LOOSE_VALVE). Then the backgrounds, a byte each (an index into BACKGROUND_TABLE), up to an $FF; then the objects in groups, a header byte (bits 0-2: how many, less one; bits 3-7: the object template, OBJECT_TABLE) and a position byte for each: U in bits 0-2, V in bits 3-5, the level in bits 6-7. A header with template 0 sets the placement nudge (PLACE_NUDGE) from the byte after it, and one with template 31 moves on to the second page of templates. Nothing ends a record but the count at +1 running out, and a group can be cut short by it.

Each room is an entry of its own, laid out from the game's data when the disassembly is built.