# Open Sosaria: reconstructing the 1981 Apple II Ultima engine

> Open Sosaria reimplements the 1981 Apple II Ultima engine in C99 for modern PCs. It parses the player's DOS 3.3 disk images, reconstructs game systems from observed behavior, and synthesizes some audio from disassembled 6502 timing loops; the author reports that the game can be completed.

- Type: Case study
- Targets: Game
- Category: Independent reconstruction cases
- Relationship: Independent reconstruction project
- Sources reviewed: 2026-11-06
- Added to the catalog: 2026-11-09
- Original resource: <https://github.com/delcodigo/open-sosaria>
- Primary source: <https://github.com/delcodigo/open-sosaria/blob/578828dc506dc9d3dd6931783ab66e1849642bad/README.md>
- Catalog page: <https://awesomerea.org/resources/open-sosaria-ultima-case/>
- Record JSON: <https://awesomerea.org/resources/open-sosaria-ultima-case/record.json>
- Chinese version: [简体中文](https://awesomerea.org/zh/resources/open-sosaria-ultima-case/index.md)

## Requirements & limits

- **Prerequisites:** Players must provide their own Apple II game disk images.
- **Prerequisites:** Building requires a C99 compiler, GLFW3, OpenGL, and GNU Make.
- **Limits:** The author reports an end-to-end beatable game and ongoing refinement of logic and rendering.
- **License:** MIT License.

## Primary sources

1. <https://github.com/delcodigo/open-sosaria/blob/578828dc506dc9d3dd6931783ab66e1849642bad/README.md>
2. <https://github.com/delcodigo/open-sosaria/blob/578828dc506dc9d3dd6931783ab66e1849642bad/docs/engine-reinterpretation-notes.md>

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## About this entry

The description was reviewed against primary sources.
Original editorial content: MIT. Linked projects, papers and assets retain their own rights and licenses.