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Sylpheed/docs/re/structures
sylph-decoder cb4fbed102 re: the keyframe block s +4 and +8 are angles used almost always as a 180 flip
Narrows a standing unexplained pair without claiming to decode it, and states
precisely why it cannot be closed in this container.

Census over every UI pak on the disc -- 2859 builds, 90347 keyframes, parents and
nested leaves. +4 has 12 distinct values and +8 has 11, against 157 for the
decoded rotation at +12. Per sprite-instance across 14241 of them, with +12 as a
control because it is known to hold a real angle: +4 takes more than two distinct
values on 7 instances, +8 on 99, and +12 on 396. So +4 is in practice a two-state
field whose state is 180 -- and for a screen-plane sprite a 180 degree rotation
about an in-plane axis is a mirror.

But they are not booleans. GP_TITLE entry 7 s ptlogo3a runs +4 = -72, -18, -4, -1
against +12 = -14, -4, -1, 0: the two decay to zero together with +4 roughly four
to five times +12 at each keyframe. That is a coupled two-axis settle and the
strongest support the disc offers for the three-axis reading. So the readings
reconcile -- the field is an angle whose overwhelmingly common use is the 180
degree special case.

The reach is the important half. All six non-zero +4/+8 keyframes in GP_TITLE are
in entry 7, the Japanese title, which has no oracle capture and which MISSION
scopes out as localisation beyond English. The five English screens that do have
captures carry +4 = +8 = 0 on every keyframe, so they never exercise the fields.
The paks that use them heavily, GP_READY_ROOM at 4686 and GP_DIALOG at 1058, are
also out of scope and GP_READY_ROOM is a recorded no-go. So this is untestable
against every oracle the project holds rather than merely unfinished.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd
2026-08-29 18:30:29 +00:00
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