Sylpheed port agent 3588a0270d docs: record what the port needs from the RE agent, ranked by cost to the port
Five items, written down here rather than only in a message, because a request
that lives in one conversation dies with the container. Two are blocking P3 (how
to recognise the splash bundle, and what the ~0.4 s fade-out actually measures),
one is cheap and prevents P5 rework (focus drawn over vs instead of the base --
the port picked replace without evidence, and the oracle says it picked wrong),
one needs a joint decision rather than a unilateral one (whether the port should
draw the newly-decoded rotation and thereby become deliberately more correct than
the renderer it verifies against), and one calibrates whether RMSE against
captures has a floor at all.
2026-08-29 08:04:38 +00:00

Sylpheed Godot

A clean-room Godot 4 port of Project Sylpheed: Arc of Deception, starting with the menu shell: developer splash → intro video → title → main menu → submenus.

You need your own copy of the game. Nothing in this repository is game content. An offline exporter reads the disc you supply and writes an open, moddable asset tree; the Godot project reads only that tree and never touches a disc format.

  your disc  ──▶  crates/sylpheed-export  ──▶  export/   ──▶  port/  (Godot 4)
                  (Rust; decoders come from      JSON + PNG        reads ONLY
                   sylpheed-formats)             + OGG + OGV       open formats

Why the wall

Two reasons, and the second is the interesting one:

  1. Godot cannot read IPFB archives, RATC bundles, T8aD textures, XMA banks or WMV video, and it should not learn to.
  2. Modding is a goal of this port. If the runtime reads the original formats, modding means reverse engineering. If it reads JSON and PNG, modding means opening a file.

Where the knowledge comes from

The decoders live in sylpheed-formats, pinned by revision — a separate project, where the reverse engineering happens. Its docs/port/HANDOFF.md is the contract: what has been decoded, what was measured off the running game, and what is known to be undecodable. Read it before assuming a value is on the disc.

Layout

crates/sylpheed-export/ disc → open formats. Regenerates export/ wholesale
port/ the Godot 4 project
authored/ decisions that are not on the disc, each with its reason
export/ generated, gitignored, never hand-edited
tools/ verification harnesses that hold the port to the reference renderer
docs/ the mission, the format spec, the agent's loop prompt

Verifying

sylpheed-cli screen render -- built from the same sylpheed-formats revision the exporter is pinned to -- is the reference renderer. tools/verify-screen draws every exported screen both ways and reports the largest per-channel difference in the frame:

tools/verify-screen              # every screen in the manifest
tools/verify-screen main_menu    # one of them

Where the two disagree, one of them is wrong; docs/DECISIONS.md says which and why, rather than tuning the port until the number goes down.

Status

P1. The exporter writes GP_TITLE's twelve screen builds and their sprites, and the Godot project draws any of them statically at 1280x720 from that tree alone. main_menu matches the reference renderer to within 3/255 on every channel of every pixel. Next: P2, keyframe animation.

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