# TH04: recover a DOS bullet-ring helper

> Inspect a 16-bit PC-98 DOS helper and relate its angle calculation to a pinned reconstruction and historical compiler checks.

- Type: Case study
- Targets: Binary · Game
- Category: Official REA: case studies
- Relationship: Official REA case study
- Sources reviewed: 2026-10-15
- Added to the catalog: 2026-10-16
- Original resource: <https://rea.tools/showcase/th04/>
- Primary source: <https://github.com/morluto/rea/blob/808339f0b1cf3837445f392b5d5f1f362d64a27d/website/evidence/th04-bullet-ring.md>
- Catalog page: <https://awesomerea.org/resources/rea-th04-case/>
- Record JSON: <https://awesomerea.org/resources/rea-th04-case/record.json>
- Chinese version: [简体中文](https://awesomerea.org/zh/resources/rea-th04-case/index.md)

## Requirements & limits

- **Prerequisites:** The matching original TH04 MAIN.EXE and the documented Ghidra DOS load profile.
- **Scope:** The showcase covers one helper.

## Primary sources

1. <https://github.com/morluto/rea/blob/808339f0b1cf3837445f392b5d5f1f362d64a27d/website/evidence/th04-bullet-ring.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.