Sylpheed port agent 753d62a08f FORMAT v3: rotation, and the focus record -- the ring the port could not reach
Pin bumped to the TAG formats-pin-2026-08-29 (76653ca), applying the policy the
previous commit wrote. What I wanted from it: `UiBuild` gained a public
`records` map. Without it a leaf was unreachable through the public API --
parse_build sorted T8aD children into `sprites` and `.rat` children into a
PRIVATE map -- so the focus ring, which lives inside ptbtn0Nf.rat, a record the
parent bundle declares NO element for, could not be located at all. My exporter
was writing 19 of build 5's 21 sprites and I could not see why.

v3 carries two new things.

ROTATION. `rotation_deg`, decoded at keyframe +12, and the game DRAWS it --
confirmed twice by the RE agent on different screens with different elements:
the title's ptloop sweeps declare +30/-45 and a GPU capture submits them at
+30.26/-45.28, and the focus ring ramps 0 -> 360 with everything else constant,
caught mid-spin in a capture. Rotation is about the DECLARED PIVOT, measured.
The comparison renderer does not draw it yet, so a rotation disagreement means
sylpheed-cli is behind, not that the port is wrong. Sign is still an assumption.

THE FOCUS RECORD. A focused button is not a sprite swap: ptbtn0Nf.rat declares
the spinning ring AND the bright label, and since the parent declares no element
for the record, the leaf is the only source of placement for both. v2's single
focus_sprite could not carry the ring at all and drew the highlight 7 px
off-centre by inheriting the base position. That -7,-7 is load-bearing: the f
label is 13 px larger per axis and -7 keeps the two concentric.

Checked against the game, not against the other renderer: rendering main_menu
with OPTIONS focused changes the region x 504..703, y 399..448. The RE agent
measured the same difference in the live capture at x 505..703, y 397..446 --
independently, from the other side. Ring, label and underline all land; the only
visible residual is the ring's spin PHASE, which is exactly the one thing
neither of us has resolved (its second keyframe is untimed, and the screen-level
rule for that is not established to apply inside a leaf). Listed in `unresolved`
rather than invented.

verify-screen is unchanged at 16/16 -- rotation has no effect at rest on these
screens, as predicted.
2026-08-29 09:04:47 +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

The oracle is the Xenia Canary capture and the game, not either renderer. sylpheed-cli screen render is an explorer and extraction CLI for verifying decodes, and it can be wrong -- three times both it and the port agreed and both were wrong, each caught only by a capture.

So tools/verify-screen is a consistency check and a regression detector, not a grade. It draws every exported screen both ways -- built from the same sylpheed-formats revision the exporter is pinned to -- 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

A difference means the two moved apart; docs/DECISIONS.md says which one moved and why, rather than tuning the port until the number goes down. Correctness is checked against the captures indexed at docs/re/captures/ORACLE-CAPTURES.md -- mind that they are not gamma-neutral, so RMSE against them has a floor.

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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