re: DIFFICULTY is a dialog -- DLG_SELECT_DIFFICULTY, GP_DIALOG entries 2/3

Closes a negative of mine whose failed assumption I had named: I searched for an
8-record btn-named build in an archive of its own, assuming DIFFICULTY's four items
pair with f variants the way GP_TITLE's screens do. It has its own prefix and is
not a GamePart screen at all.

Three independent routes agree. The image lists DLG_SELECT_DIFFICULTY among the
DLG_* dialog names at 0x820A41BB, and GP_DIFFICULTY appears zero times. GP_DIALOG
entries 2/3 are the only builds there with pcbtn00..03 -- four buttons at design
rows 259/329/399/469, spacing 70, an EN/JP pair. And my capture of the running
screen puts its four rows within 4 px of those, with spacing 70.5/69.5/70.0 against
the disc's 70/70/70.

Reach stated: the entries are identified by button count and geometry, not by a
binding from the DLG_ name to a pak entry. No such binding was found.

Also notes the consequence for Q6's count-match: NEW GAME opens a DIALOG from an
external archive, which still matches the count but is not the same category as
OPTIONS or TUTORIAL opening a GamePart.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wuu56cE8vJGTBtn1ppsk8v

docs/re/data/difficulty-is-a-dialog.txt

@@ -0,0 +1,66 @@
+# Where does the DIFFICULTY screen live? ✅ DECODED 2026-08-31.
+# It is a DIALOG -- `DLG_SELECT_DIFFICULTY`, GP_DIALOG.pak entries 2/3.
+#
+# CLOSES A NEGATIVE OF MINE. gp-title-holds-three-button-screens.txt recorded
+# "not an 8-record btn-named build anywhere on the disc", with the failed
+# assumption named as mine: I assumed DIFFICULTY's four items pair with `f` focus
+# variants in an archive of its own, the way GP_TITLE's screens do. Both halves
+# of that were wrong -- it has its own button prefix and it is not a GamePart
+# screen at all.
+#
+################################################################################
+# ROUTE 1 -- THE IMAGE. /image/sylpheed.pe, 3 occurrences of "DIFFICULTY":
+#   0x820A2548  STAGE | DIFFICULTY | TITLE | FADE | BASE_EXTRA ...
+#               (a GamePartTask::RegisterToFactory name list)
+#   0x820A3377  RECORD_DIFFICULTY   (a results/record field)
+#   0x820A41BB  DLG_LEADERBOARD_MENU_NEXT | DLG_SYSTEM_PAUSE |
+#               **DLG_SELECT_DIFFICULTY** | DLG_MISSION_OBJECTIVE |
+#               DLG_MESSAGE_BOX | DLG_MESSAGE_BOX_YES_NO | ...
+#
+# ✅ The third is the answer: DIFFICULTY is one of the game's DLG_* dialogs.
+# ⚠️ "GP_DIFFICULTY" appears 0 times in the image, which is consistent.
+#
+################################################################################
+# ROUTE 2 -- THE DISC. GP_DIALOG.pak entries 2 and 3 are the only builds in that
+# archive carrying `pcbtn00`..`pcbtn03` -- FOUR buttons, matching
+# EASY / NORMAL / HARD / BACK. Design rows and spacing:
+#
+#   entry 2   y 259 / 329 / 399 / 469     spacing 70, 70, 70
+#   entry 3   identical                    (the EN/JP pair, as everywhere else)
+#
+# ✅ CONTROL: the same reader on GP_TITLE entry 5 returns 162/242/322/401/482,
+# spacing 80 -- the rows that archive is independently known to place.
+#
+################################################################################
+# ROUTE 3 -- THE ORACLE. My own capture of the running DIFFICULTY screen
+# (captures/menu-nav/live-difficulty-opens-normal.png), with the disc-grounded
+# calibration capture_y = 64.82 + 0.9919 * design_y:
+#
+#   design row   predicted    measured in the capture   residual
+#      259         321.7            323.5                +1.8
+#      329         391.2            394.0                +2.8
+#      399         460.6            463.5                +2.9
+#      469         530.0            533.5                +3.5
+#   measured spacing 70.5 / 69.5 / 70.0  against the disc's 70 / 70 / 70
+#
+# Four rows, all under 4 px, with the spacing agreeing exactly. The residual is a
+# uniform ~+2.8 px offset, which is the calibration's own systematic and not a
+# mismatch.
+#
+# => THREE INDEPENDENT ROUTES: the executable names it a dialog, the disc has a
+#    four-button dialog build, and the running game draws its rows where that
+#    build says they are.
+#
+# 📌 WHY IT MATTERS BEYOND THE LOCATION: DIFFICULTY being a DIALOG explains why
+# NEW GAME's destination is not a screen in GP_TITLE, and it means the "four menu
+# items load an external archive" reading of the event numbers
+# (boot-config-and-gamepart-registry.md's count-match) is looser than it looked --
+# NEW GAME opens a dialog from GP_DIALOG.pak, which is an external archive, but a
+# dialog is not the same kind of thing as OPTIONS or TUTORIAL opening a GamePart.
+# The count still matches; the categories are not uniform.
+#
+# ⚠️ REACH: entries 2/3 are identified by button count and geometry, not by a
+# name binding DLG_SELECT_DIFFICULTY to a pak entry. No such binding was found --
+# the DLG_* names live in a string list, and what maps a name to an archive entry
+# is not decoded. Another 4-button dialog with the same rows would be
+# indistinguishable by this evidence.