ANATOMIST

A real 32 KB Game Boy cartridge. The free browser demo is right here on this page — floors one to four, no download, no account.

Updated to 1.2.0: descending now shows a DEPTH card instead of a blank screen, the depth number reads as a number, death and the win fade to black, and the browser demo runs at Game Boy speed on any monitor. The sequel is out: ANATOMIST II: GRAFT ($5.99), where you kill a monster and wear one of its parts.

You descend a dungeon whose every monster is composed while you play, out of authored body parts, and the nine tells below are the rules. The rest of the body — most heads, and the wings and tail on a creature’s back — is variety, not information.

• Many legs — it moves twice for every step you take.
• Roots instead of legs — it never moves at all. A hazard, not a hunter.
• A scythe arm — it reaches one square further than you expect.
• A stub where an arm should be — it cannot hurt you. Walk past it.
• A shell on its back — the first hit you land does half damage.
• Spines on its back — hitting it costs you a life. Every time.
• A heavy torso — six life. A gaunt one — two.
• No eyes — it is blind: once awake it wanders instead of coming for you, until you are beside it.

There is no bestiary to memorise, because there is no fixed bestiary. The cartridge can build 8,640 different creatures and composes a fresh set on every floor.

What carries between runs is not a stat or an unlock. It is knowing what a shape means.

Monsters sleep until you come within two squares, or until you hit one. That is the whole game: read the silhouette, and decide whether this one is worth waking. Every floor composes creature types that differ in arm and in base; which of them you meet, and how many of each, is left to chance.

Ten floors. Eight lives. A staircase gives three back, and it is the only rest there is.

Clear the tenth and you surface. It is hard — instrumented bots that ignore the shapes entirely die on floor two, and the game is built on the assumption that you will not.

The cartridge draws its own monsters

This is the part worth paying for. The ROM carries 418 bytes of authored part masks — no sprite sheet, no atlas, not one pre-rendered creature — and a 4 MHz CPU composes, welds, form-shadows and outlines any of 8,640 of them while you play. Baking in a fixed set would have been smaller and simpler. It would also have been a different game.

The dungeon is built from an authored 8×8 tile alphabet in four shades. Every sound is written to the Game Boy’s own four sound channels — two pulse channels, a wave channel and a noise channel — because there is nowhere in 32,768 bytes to put a sample, and no need.

It is a real .gb ROM

Standard ROM-only, no mapper, valid header, checked on the bytes of every build. It is tested in the binjgb emulator, the same one that runs the free demo on this page. Other emulators and physical hardware are untested, so we make no claim about them.

Controls

ARROWS / D-PAD move, or attack whatever is there · ENTER / START begin · Z / A continue · RIGHT SHIFT / SELECT mute. That is the whole scheme. There is no menu.

What you get

Free, on this page: the browser demo — floors 1–4, the same cartridge, running on the binjgb emulator.
$4.99: anatomist.gb — the full ten-floor cartridge, 32,768 bytes, a standard ROM-only file, tested in binjgb.

Honest notes

It is difficult, runs are short and permadeath is permanent. There is no save — a run is a run, and the mute setting lasts until you power off.

Made with AI, and tagged truthfully on this page. The sounds are not tagged, because there are no audio files in this cartridge at all: every sound is the console's own synthesiser being driven by register writes, which itch's own guidelines exempt from generative-AI tagging.

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Made by Core Systems Asset Factory, which also builds engine tooling and art packs for RPG Maker, GameMaker, Unity and Unreal — csaf.itch.io

More games from CSAF

• NOCTUARY — a picross cabinet of moths that do not exist. 66 plates, every one solvable by logic alone.
• THE BRASS ORRERY — a star is not a tree. You do not climb it; you close shapes in it.
• WICKLIGHT — you are the light. They live in your shadow.
• ANTIPOLE — one button. You have no engine, only a sign.

We also make the parts

Core Systems Asset Factory builds pixel-art packs and engine tooling for developers:

• VERDANT 01 — Overworld — 239 tiles and four complete 47-mask autotile sets, for RPG Maker MZ, Tiled and Godot.
• MOURNCREST 02 — The Pale Choir — five cultists, four directions, three-frame walks, at native 64px and 128px.
• VERDANT 00 — free sample pack — 64 tiles with one complete autotile, free, if you want to try them first.

Plus plugins and editor tools for RPG Maker MZ, GameMaker, Unity and Unreal — the full catalogue is here.