// The manor

A flip-screen castle, in isometric view

One room fills the screen and nothing scrolls — the one shape of game the 2600 is genuinely good at. Each room is drawn isometrically: a diamond of paved floor, two walls along its far edges with arched doorways in them, the near edges open.

Almost all of the castle survives the trip: 152 rooms, 401 doors, eleven trapdoors with the carpets they drop you onto, and twelve staircase rooms. The map is not retyped for the 2600 — it is read from the same file as the Vectrex and desktop versions of the game.

The footage at the top is recorded from the ROM: the title screen, then a route through the manor planned door to door by the game's own logic.

// Rooms

Every room its own colour

Wandering ghosts, bats and spiders, one species to a room. Guardians who chase you. Doors that open and shut, locked doors that want the right key, trapdoors in the paving, and things to find along the way.

// How it works

Two layers, one picture

The floor is one colour and the walls another, and a 2600 playfield has one colour per scanline. The answer is Zaxxon's: the floor is drawn on the even scanlines and the walls on the odd ones. Each layer is half as dense as it could be, each has its own colour on every line it owns, and the eye puts them back together.

The cartridge is a CDFJ image: an ARM beside the 6507. The ARM draws the room into a 40 × 192 bitmap and packs it into eleven data streams. The 6507 reads the streams and writes them to the TIA, twelve updates a line, and does no arithmetic at all. Gameplay costs the display nothing.

// The book behind it

How it was made, chapter by chapter

ATARI 2600 MASTERY tells how a game like this is built: C on the Melody's ARM, 6507 assembly on the line, every number measured. Its last chapter is the book edition of DUSK MANOR, grown across all thirty-eight chapters.