Touhou TH04 / PC-98 / REA / N0zoM1z0 / EN
Recover a bullet-ring calculation from 16-bit code
ENGLISH SUMMARY
Recover a bullet-ring calculation from 16-bit code
Inspect a PC-98 game's angle helper and connect its arithmetic to a readable C++ reconstruction of fixed and aimed bullet rings.
The question
How does the bullet ring choose an aiming angle from the player's position?
The workflow
- Inspect the original DOS program's 16-bit function.
- Map coordinates, multiplication, and division to C++.
- Check the reconstruction against historical compiler output.
Findings & output
The official case presents the recovered angle calculation and links a public reconstruction repository.
Evidence scope
This entry concerns an angle helper, without extending the result to a fully verified reconstruction of the whole game.
中文摘要
从 16 位指令，恢复弹幕瞄准计算
检查 PC-98 游戏的角度计算，把乘除法与坐标运算整理成 C++，理解固定与瞄准弹幕的生成规则。
调查的问题
弹幕环怎样根据玩家坐标确定瞄准角度？
怎么做的
- 分析原始 DOS 程序的 16 位函数。
- 把坐标、乘法与除法对应到 C++。
- 结合历史编译器输出检查重建。
发现与产出
官方案例展示了恢复的角度算法，并链接公开重建仓库。
证据范围
此条关注角度辅助函数；不把局部重建结论推广为整款游戏都已验证。
Original sources / 原始来源
Checked / 核对 2026-10-12 · Public code / 有公开代码