AGI IS HERE

AGI is here, and it runs in your browser. It understands commands like LOOK AT CASTLE, it draws in sixteen colours, and if you ask, it will put an alligator in the moat while you are standing next to it.

This AGI is Sierra's Adventure Game Interpreter, the engine behind King's Quest, Space Quest and Leisure Suit Larry, rebuilt from scratch. Play the classics from your own copies, build a game by hand, or describe an adventure and play it while an AI agent builds the world around you. Everything you make is a real AGI game that you can inspect, download and play again.

One brief, five models. Each castle is a real AGI picture drawn in vector commands, with a working moat, a hero and a game behind it, for between three cents and two dollars. From the Genesis benchmark.

Try it

Open agi.monotio.com and choose Play the tutorial. Adventure Department is a three-room tutorial about how these games are made: you repair a picture, wake up an actor and sort out a clerk's Priority.

• Play your own Sierra games. Add game takes a game folder, a ZIP or its disk images; add all disks of a game together. The files stay in your browser, and the app picks the matching interpreter for the edition.
• Watch a walkthrough. Verified releases replay a recorded completion on the engine. Pause it, scrub the timeline, or Take control.
• Rewind. Every session records itself, so you can return to any earlier moment and carry on from there.
• Get help. Help on the home screen and in a running game explains playing, creating and managing games.

The games it plays

These editions are verified in this interpreter. The PC editions are checked with recorded walkthroughs; the Amiga and Apple IIgs editions boot into their first room under their own interpreters.

Game	PC (DOS)	Amiga	Apple IIgs	Recorded walkthrough
King's Quest I	Yes			Full game
King's Quest II	Yes	Yes		Full game
King's Quest III	Yes			Full game
King's Quest IV	Yes			Full game
Space Quest I	Yes	Yes		Full game
Space Quest II	Yes	Yes	Yes	Full game
Police Quest I	Yes	Yes		Full game
Leisure Suit Larry I	Yes			Full game
The Black Cauldron	Yes			Full game
Mixed-Up Mother Goose	Yes			Full game
Donald Duck's Playground	Yes			One chapter
Gold Rush!	Yes	Yes		Full game
Manhunter: New York	Yes			Full game
Manhunter 2: San Francisco	Yes	Yes		Full game
Sierra AGI demo pack 4	Yes

Sound follows the machine: emulated Paula on the Amiga, Ensoniq wavetable on the IIgs, and the Tandy chip or PC speaker on a PC. Settings → Advanced… → Sound chip picks the PC one. The picture fills the frame its original monitor showed: 4:3 for a PC, IIgs or NTSC Amiga game, a little wider for a PAL Amiga. Turn off Settings → Original proportions for square pixels. Mouse clicks walk the hero on the Amiga and IIgs. Connected gamepads follow the game's own joystick controls, and on a phone, Keys offers function, modified letter and fire-button keys. Amiga and IIgs games use their own palettes, fonts and status line. PC text uses this project's own 8 × 8 font, a pixel-for-pixel recreation of the original BIOS typeface. A game's own AGIFONT file is used when the player's copy has one. Native IIgs menus and the Standard File dialog, and the Hercules and composite displays, are not built yet. Fan-made games run too. Testing compatibility lists the exact editions, disk-image formats and builds.

Bring your own copies of commercial games. Fans have also made over a hundred free AGI games since the late nineties. Find them on the AGI Wiki's fan release list and the SCI Programming community's game list.

Make your own game

Make a new game offers four starts. Starter is a sunny clearing with a hero. Boilerplate has the menus, saving and game-over code for your own rooms. Blank is empty, and Create with AI asks an agent to begin. The game opens in Create. It keeps running on the stage while you edit its pictures, characters, code, words and sounds beside it. Edits save as you go, Update and restart puts them in the game, and Undo works across every part.

PICTURE, LOGIC with Problems, Agent review, and VIEW with cels from an image. The media gallery shows more.

• Build your first game walks through a first edit in each editor.
• The Create workspace covers every editor, Launches, the debugger and the keyboard shortcuts.

Build with AI

Connect an OpenAI or Anthropic API key and the agent becomes a co-author. Create with AI plans a world from a themed brief or your own idea and builds the opening room. When you walk into a room that does not exist yet, play pauses while the agent writes it.

In Play the agent gives hints and answers questions. In Create it changes any part of the game with you, shows previews of each change, and applies them as one History step. Requests go from your browser straight to your provider and are billed to your account; each task has a budget you can change. Building with AI covers templates, reviews, budgets and privacy.

Save and share

Games, saves and history live in your browser. The game's own Save and Restore keep their files in the app. The engine reads and writes original .SAV files for every build except the 2.001 booter; importing them in the app is planned. The app also saves as you play, so Resume picks up where you left off.

Settings → This game → Download…	What you get
Project file	A ZIP of the project with available conversation, images, source descriptions, world notes, tests, map, history, saved games and autosave. A backup reports limitations, including omitted pending edits and unavailable progress.
Playable game	A ZIP of the playable resources and public metadata: description, author, license and remix provenance.

Either ZIP opens again with Add game, in any browser.

Thirty years later

Around 1996, Lance Ewing, Peter Kelly, Martin Tillenius and I worked on MEKA, an early fan-made AGI interpreter. I was Joakim Möller then. We traded discoveries about how Sierra's adventures worked.

On 3 September 2026, Greg Brockman closed an OpenAI briefing with “Welcome to the AGI era.” I took him at his word. With OpenAI's GPT-6 Astra in Codex, I went back to AGI to rebuild the engine, and to let an agent change the game while I was playing it. Now I can ask for an alligator in the moat, and the agent rewrites the game's own bytecode to put it there. Thirty years on, that is still a very cool thing to be able to do.

Peter Kelly's agi-re behavioral specification is the foundation of this independent implementation. It documents the formats, observable behavior and interpreter versions, and is published under CC0. Thank you, Peter.

Checked against the originals

Every Sierra AGI game shipped with its own build of the interpreter, and the builds do not quite agree. The 22 original builds we read run as 18 profiles, because a few builds behave like a sibling build and share its profile. Police Quest's PC build 2.903 is one of them: it behaves like 2.917 on everything verified, so EQUIVALENT_BUILDS maps it to the 2.917 profile. On a PC, a wandering guard whose countdown runs out walks 256 more steps before he turns; on an Amiga he turns every 7 to 51 steps. Details like that decide whether a puzzle is fair, so the engine keeps them.

Sometimes a game needs more than the specification says, or builds disagree. Then the original interpreters' machine code was read, and often run with controlled inputs. That covers PC builds 2.089 to 3.002.149, the Amiga and the Apple IIgs. Each finding is written down with its evidence and held in place by a test. Some gaps remain: the fidelity notes' coverage table lists the evidence behind each aspect and what is still missing. Full-game walkthroughs of thirteen games replay keystroke by keystroke. Interpreter compatibility tells the whole story.

The engine is a TypeScript AGI interpreter with no runtime dependencies. It reads AGI v2 and v3 games, including the Amiga and Apple IIgs layouts, and runs in a Web Worker. Games made in the app are standard AGI 2.936 bytecode with no custom opcodes.

How it's built

Coding agents build this project, alongside the agent inside it, and the repository checks the work of both. AGENTS.md is the working agreement every contributor follows, person or agent. The in-app agent can only call the tools on its session's allowlist, and the assembler and resource checks validate everything it writes. A model mistake that recurs becomes a stored eval case that replays offline on every check.

npm run check is the gate: typecheckers, linters, structural rules, the engine and app tests and the stored evals. CI adds Playwright in Chromium and WebKit. Contributing maps the code and explains each check. The LOGIC language server gives any LSP editor the same code intelligence as the LOGIC editor.

Run it yourself

Install Node.js 22.22 or newer, then:

npm ci
npm run dev

Open http://localhost:5199/. The site needs a connection to load; exported games play offline in any compatible interpreter. The documentation index lists the guides, including self-hosting.

License

Created by Joakim Riedel and published by Monotio. The engine, authoring tools, browser shell and original project assets, including the Adventure Department tutorial, use the MIT license. The bundled UI fonts use the SIL Open Font License 1.1, with attribution in NOTICE. The icons are a hand-picked Lucide set under ISC and Feather MIT notices. Dependencies and imported games keep their own licenses, and no commercial game assets are part of this repository. A game without a declared license keeps an unknown license in its exports.