Open source platform

Build books for Fortress Reader.

Fortress Reader is an open source platform for interactive books. Anyone can write adventures that support the reader, build compatible tools, and ship Fortress-format stories. There is no royalty due.

Public format spec TypeScript types Conformance fixtures AI-agent friendly No royalty

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fortress-adventure.json schema 1.1

{
  "title": "The Alchemist's Crypt",
  "rootScene": "crypt-door",
  "scenes": [{
    "id": "crypt-door",
    "text": "The lock clicks.",
    "choices": [{
      "label": "Open the iron door",
      "to": "flooded-stair",
      "requires": ["skeleton-key"]
    }]
  }]
}

Developer downloads

Specs, sample code, and test fixtures.

These files define the public Fortress adventure package format and give developers a repeatable way to create and validate compatible books.

Format spec

The canonical `.fortress.zip` package structure, manifest rules, artifacts, scenes, gates, and compatibility expectations.

Download spec

TypeScript types

Strongly typed wire and authoring models for tools, compilers, generators, and AI-assisted book creation workflows.

Download types

Conformance suite

Fixture ZIPs and build scripts for checking that a reader, importer, or publishing pipeline handles the format correctly.

Download complete kit

AI agent prompts

Starter prompts for authoring adventures, compiling them into the wire format, and checking packages before release.

Download prompts

For authors and tool builders

Make interactive books without asking permission.

Fortress adventures are ordinary distributable files. Write by hand, generate with code, or ask an AI agent to draft scenes against the public types and spec.

Use the public spec. Package scenes, artifacts, choices, and validation metadata into a Fortress adventure ZIP.
Start from typed models. Use the TypeScript definitions as the contract for generators and authoring tools.
Validate behavior. Run the conformance fixtures to catch bad hashes, dangling edges, missing artifacts, and version mismatches.
Prompt AI agents clearly. Tell an agent to emit Fortress authoring JSON using the included types, then compile and validate before release.

Complete kit

One download.

Download the full open source kit with the format spec, TypeScript types, conformance fixtures, sample packages, and AI-agent starter prompts.

Download open source kit

No royalty due

Write the book. Ship the adventure.

The Reader audience can keep using the simple install page. Developers can use this open source kit to create compatible Fortress adventures for them.

Download the kit