port: the PRESS (A) plate pulses -- authored per element, because 82 of 212 share its shape

The human listed pulsation as first-class and the port drew nothing: the plate's
focus record `ptbtn00f` was never reached, because press_start has no `buttons`
and nothing is focused. That it LOOPS is measured -- the corpus timed the period
four times (2.12 / 2.19 / 2.34 / 2.31 s) and you cannot measure a period unless
the thing repeats.

THE RULE I WAS GOING TO WRITE DIED IN THE CENSUS. The spinning ring is a rule in
the renderer because it has a disc-wide check: 16 of 212 elements match its shape
and all 16 are focus rings. The analogous shape for a pulse -- keyframes varying
only in alpha, first alpha equal to last -- matches 82 OF 212, including
ptcopyright, palogo_sqex, ptmsg and every _eff fade. A renderer rule on it would
make the copyright notice pulse. Narrowed to focus records it matches exactly one
distinct element, and a rule justified by n=1 is a special case wearing a rule's
clothes.

So it is a LOOKUP in authored/timing.json keyed <screen>/<element>, with the
census recorded beside it so nobody widens it later.

The period is 129 units -- the element's own group under the port's existing
model: last timed keyframe t=105 plus the authored exit_ramp_units of 24. No new
constant. 2.150 s at 60 units/s, 2.295 s at the ~28.1 fps the emulator presents,
against measurements of 2.12-2.34.

IT IS A CHOICE AND THE ALTERNATIVE IS STATED: restarting at the group's first
keyframe (t=6) instead of 0 gives 123 units = 2.050 / 2.189 s, also inside the
measured spread. Nothing separates them. t=0 is taken because it is where every
other group starts -- consistency, not evidence.

Verified the way the ring was, by bit-identity one period apart. 20 periods is
43.00 s = exactly 172 film frames: frames N and N+172 differ by 0-1/255, while
the control a quarter-second off (43.25 s) differs by 58.7/255. On the held boot
title the glow-box mean swings 26.0 <-> 37.7.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N7FiFFFwbvG2uxdcEh8HyF

port/scripts/boot.gd

@@ -178,8 +178,13 @@ func _ready() -> void:
 	# The one unknown duration per screen: the ramp into the final untimed
 	# keyframe. Authored, because the disc has no time slot there.
 	view.exit_ramp_units = float(timing["exit_ramp_units"])
+	# Which focus records draw unconditionally and loop. Kept out of ScreenView's
+	# own logic on purpose -- see `looping_focus` there for the census that says
+	# this cannot be a rule.
+	_looping = timing.get("looping_focus_records", {})
 	viewport.add_child(view)
 
+	view.looping_focus = _looping_for(name)
 	if not view.load_screen(export_tree, name):
 		push_error(export_tree.error)
 		get_tree().quit(2)
@@ -241,6 +246,8 @@ var _flow: Variant = null
 var _menu: MenuFlow = null
 var _play := false
 var _pending: Variant = null
+## `authored/timing.json` `looping_focus_records`, keyed `<screen>/<element>`.
+var _looping: Dictionary = {}
 var _script: PackedStringArray = PackedStringArray()
 var _shots := ""
 ## `--skip-at=SECONDS`: when to send a synthetic (A) during a movie, or 0.
@@ -340,6 +347,7 @@ func _advance() -> void:
 	print("  -> %s at %.2f s" % [name, _elapsed])
 	view.holding = true
 	view.time_units = 0.0
+	view.looping_focus = _looping_for(name)
 	if not view.load_screen(view.tree, name):
 		push_error(view.tree.error)
 		get_tree().quit(2)
@@ -541,6 +549,7 @@ func _menu_arrive() -> void:
 	var name := String(action["goto"])
 	view.holding = true
 	view.time_units = 0.0
+	view.looping_focus = _looping_for(name)
 	if not view.load_screen(view.tree, name):
 		push_error(view.tree.error)
 		get_tree().quit(2)
@@ -854,6 +863,7 @@ func _raise_overlay(name: String) -> void:
 	overlay.texture_filter = CanvasItem.TEXTURE_FILTER_NEAREST
 	overlay.units_per_second = view.units_per_second
 	overlay.exit_ramp_units = view.exit_ramp_units
+	overlay.looping_focus = _looping_for(name)
 	overlay.holding = true
 	overlay.time_units = 0.0
 	if not overlay.load_screen(view.tree, name):
@@ -925,3 +935,19 @@ func _finish_boot() -> void:
 
 
 var _capture_to := ""
+
+
+## The authored looping-focus entries that apply to one screen.
+##
+## The table is keyed `<screen>/<element>` so a reader can see at a glance which
+## screen an entry belongs to -- `ptbtn00` exists on more than one build, and an
+## entry that silently applied to all of them would be a rule again.
+func _looping_for(screen_name: String) -> Dictionary:
+	var out := {}
+	for key: String in _looping.keys():
+		if key == "_":
+			continue
+		var parts := key.split("/", true, 1)
+		if parts.size() == 2 and parts[0] == screen_name:
+			out[parts[1]] = _looping[key]
+	return out

port/scripts/screen_view.gd

@@ -42,6 +42,22 @@ var units_per_second: float = 60.0
 ## that keyframe, so this is the one unknown duration per screen.
 var exit_ramp_units: float = 24.0
 
+## Focus records this screen draws unconditionally, and the period each loops on.
+##
+## `{ <parent element id>: { "record_element": String, "period_units": float } }`,
+## from `authored/timing.json` `looping_focus_records`, keyed there by
+## `<screen>/<element>` and narrowed to this screen by `load_screen`.
+##
+## ⚠️ A LOOKUP, NOT A RULE, and the census is why. The spinning ring is a rule
+## (`spin_period_units`) because 16 of 212 elements match its shape and all 16
+## are focus rings. The analogous rule for a pulse -- keyframes varying only in
+## alpha, first alpha equal to last -- matches **82 of 212**, including
+## `ptcopyright`, `palogo_sqex`, `ptmsg` and every `_eff` fade. It would make the
+## copyright notice pulse. Narrowed to focus records it matches exactly one
+## distinct element, and a rule justified by n=1 is a special case wearing a
+## rule's clothes.
+var looping_focus: Dictionary = {}
+
 ## While true the screen holds at `rest` and never plays its exit. The
 ## sequencer clears it to send the screen away.
 var holding: bool = true
@@ -353,6 +369,7 @@ static func _rot_of(pose: Dictionary) -> float:
 ## down-right and off-centre.
 func _draw_focus(element: Dictionary) -> void:
 	var focus: Dictionary = element.get("focus", {})
+	var parent_id := String(element.get("id", ""))
 	for fe: Dictionary in focus.get("elements", []):
 		var rel: String = fe.get("sprite", "")
 		if rel == "":
@@ -377,6 +394,19 @@ func _draw_focus(element: Dictionary) -> void:
 		# and what the RE agent supplied is that one turn takes exactly that
 		# long and repeats. See `spin_period_units` for the rule and its check.
 		var pose: Dictionary = fe.get("rest", {})
+		# An authored loop plays the record's OWN group on repeat instead of
+		# holding it at rest. `pose_at` already synthesises the final untimed
+		# keyframe at `exit_ramp_units`, so a loop is a modulo and nothing else --
+		# no new machinery and no new constant. `holding` is bypassed for the
+		# same reason the ring bypasses it: a thing that pulses does not stop
+		# because the screen has arrived.
+		var loop: Dictionary = looping_focus.get(parent_id, {})
+		if float(loop.get("period_units", 0.0)) > 0.0 \
+				and String(loop.get("record_element", "")) == String(fe.get("id", "")):
+			var was := holding
+			holding = false
+			pose = pose_at(fe, fposmod(time_units, float(loop["period_units"])))
+			holding = was
 		var pivot := _vec(fe.get("pivot", [0, 0]))
 		var pos := _vec(pose.get("pos", [0, 0]))
 		var period := spin_period_units(fe)
@@ -413,8 +443,11 @@ func _draw() -> void:
 		var pivot := _vec(element.get("pivot", [0, 0]))
 		var pos := _vec(pose.get("pos", [0, 0]))
 		var rot := _rot_of(pose)
-		# A focused button draws its own record instead of its base sprite.
-		if focused_id == id and element.has("focus"):
+		# A focused button draws its own record instead of its base sprite -- and
+		# so does an element the authored table says always shows it, which is
+		# how the PRESS (A) plate gets its glow on a screen that has no buttons
+		# and focuses nothing.
+		if (focused_id == id or looping_focus.has(id)) and element.has("focus"):
 			_draw_focus(element)
 			continue
 		var rel: String = element.get("sprite", "")