explore: pivot to noclip free-roam camera

Ground-truth from render_overworld.py showed Kanto is ONE seamless world joined
along shared edges with per-connection offsets -- so a map-by-map browser is the
wrong model. Replaced it with noclip free-roam that leans on the engine's own
player-walk + connection-crossing machinery (which already handles seams/offsets
correctly):

- wSlopNoclip flag (reused the dead wUnusedObtainedBadges byte at D356, 0 r/w,
  not unioned, in the saved region -> safe).
- CollisionCheckOnLand: 5-byte hook at the top -> when noclip is set, return
  no-collision. Freed the room in ROM0 by deleting the unreferenced Func_0db5
  (dead farcall LoadToggleableObjectData) in LoadMapHeader.
- EXPLORE menu entry now just toggles wSlopNoclip and closes the menu, dropping
  you into the overworld to glide through walls/NPCs/ledges and walk across map
  connections exactly as the world data defines them.

Verified: Pallet -> (walk north through the fences) -> seam-cross into Route 1 at
y=35 -> continue north; toggle off restores collision (player blocked).

4 files changed, 17 insertions, 148 deletions

diff --git a/engine/movie/oak_speech/init_player_data.asm b/engine/movie/oak_speech/init_player_data.asm
index 90fb8f0e..589f4b5f 100644
--- a/engine/movie/oak_speech/init_player_data.asm
+++ b/engine/movie/oak_speech/init_player_data.asm
@@ -39,7 +39,7 @@ DEF START_MONEY EQU $3000
 
 	ld hl, wObtainedBadges
 	ld [hli], a
-	ASSERT wObtainedBadges + 1 == wUnusedObtainedBadges
+	ASSERT wObtainedBadges + 1 == wSlopNoclip
 	ld [hl], a
 
 	ld hl, wPlayerCoins
diff --git a/engine/slop_menu.asm b/engine/slop_menu.asm
index fcac7d10..e3b07fe6 100644
--- a/engine/slop_menu.asm
+++ b/engine/slop_menu.asm
@@ -221,149 +221,17 @@ WarpMapTable:
 ; (via wCurMapConnections + the connection headers). B restores the original
 ; map and returns to the SL0P menu. No warping yet - read-only browse.
 ; ===========================================================================
+; ===========================================================================
+; EXPLORE: toggle noclip free-roam. With noclip on, CollisionCheckOnLand is
+; bypassed, so you glide through walls / NPCs / ledges and cross map connection
+; seams exactly as the world data defines them. Closes the menu so you drop
+; straight back into the overworld to roam. Pick it again to turn it off.
+; ===========================================================================
 SlopExplore:
-; save origin map + coords on the stack
-	ld a, [wYCoord]
-	ld b, a
-	ld a, [wXCoord]
-	ld c, a
-	push bc                        ; origin Y,X
-	ld a, [wCurrentTileBlockMapViewPointer]
-	ld b, a
-	ld a, [wCurrentTileBlockMapViewPointer + 1]
-	ld c, a
-	push bc                        ; origin view pointer
-	ld a, [wCurMap]
-	push af                        ; origin map
-.render
-; LoadMapData loads the map header + block map into wOverworldMap, but it renders
-; using a STALE wCurrentTileBlockMapViewPointer -- the game only ever sets that
-; from warp / connection / walk data, never from wXCoord/wYCoord. So load the
-; map, then compute a centered view pointer ourselves and redraw the view.
-	call LoadMapData
-; stride = wCurMapWidth + MAP_BORDER*2 ; bufRow = height/2 + 1 ; bufCol = width/2
-; wCurrentTileBlockMapViewPointer = wOverworldMap + bufRow*stride + bufCol
-	ld a, [wCurMapWidth]
-	add MAP_BORDER * 2
-	ld c, a
-	ld b, 0                        ; bc = row stride (blocks)
-	ld hl, 0
-	ld a, [wCurMapHeight]
-	srl a
-	inc a                          ; bufRow (>= 1)
-.viewRowLoop
-	add hl, bc
-	dec a
-	jr nz, .viewRowLoop
-	ld a, [wCurMapWidth]
-	srl a                          ; bufCol = width/2
-	add l
-	ld l, a
-	jr nc, .viewNoCarry
-	inc h
-.viewNoCarry
-	ld bc, wOverworldMap
-	add hl, bc
-	ld a, l
-	ld [wCurrentTileBlockMapViewPointer], a
-	ld a, h
-	ld [wCurrentTileBlockMapViewPointer + 1], a
-	xor a
-	ld [wYBlockCoord], a
-	ld [wXBlockCoord], a
-	call LoadCurrentMapView        ; redraw wTileMap centered on the map
-	ldh a, [rLCDC]                 ; hide ALL sprites (player + actors) via LCDC
-	res B_LCDC_OBJS, a
-	ldh [rLCDC], a
-	ld a, $90
-	ldh [hWY], a                   ; window off-screen -> the BG map is visible
-; overlay direction markers at the screen edges for the legit connections
-	call LoadFontTilePatterns
-	ld a, [wCurMapConnections]
-	ld e, a
-	bit NORTH_F, e
-	jr z, .noN
-	hlcoord 9, 0
-	ld [hl], $8D
-.noN
-	bit SOUTH_F, e
-	jr z, .noS
-	hlcoord 9, 15
-	ld [hl], $92
-.noS
-	bit WEST_F, e
-	jr z, .noW
-	hlcoord 0, 8
-	ld [hl], $96
-.noW
-	bit EAST_F, e
-	jr z, .noE
-	hlcoord 18, 8
-	ld [hl], $84
-.noE
-	ld b, HIGH(vBGMap0)
-	call CopyScreenTileBufferToVRAM  ; push map + markers to VRAM
-.input
-	call DelayFrame
-	call JoypadLowSensitivity
-	ldh a, [hJoyPressed]
-	ld d, a
-	bit B_PAD_B, d
-	jr nz, .exit
-	bit B_PAD_UP, d
-	jr z, .chkDown
-	ld a, [wCurMapConnections]
-	bit NORTH_F, a
-	jp z, .input
-	ld a, [wNorthConnectedMap]
-	ld [wCurMap], a
-	jp .render
-.chkDown
-	bit B_PAD_DOWN, d
-	jr z, .chkLeft
-	ld a, [wCurMapConnections]
-	bit SOUTH_F, a
-	jp z, .input
-	ld a, [wSouthConnectedMap]
-	ld [wCurMap], a
-	jp .render
-.chkLeft
-	bit B_PAD_LEFT, d
-	jr z, .chkRight
-	ld a, [wCurMapConnections]
-	bit WEST_F, a
-	jp z, .input
-	ld a, [wWestConnectedMap]
-	ld [wCurMap], a
-	jp .render
-.chkRight
-	bit B_PAD_RIGHT, d
-	jp z, .input
-	ld a, [wCurMapConnections]
-	bit EAST_F, a
-	jp z, .input
-	ld a, [wEastConnectedMap]
-	ld [wCurMap], a
-	jp .render
-.exit
-	pop af
-	ld [wCurMap], a               ; restore origin map
-	pop bc                        ; restore origin view pointer
-	ld a, b
-	ld [wCurrentTileBlockMapViewPointer], a
-	ld a, c
-	ld [wCurrentTileBlockMapViewPointer + 1], a
-	pop bc                        ; restore origin Y,X
-	ld a, b
-	ld [wYCoord], a
-	and $1
-	ld [wYBlockCoord], a
-	ld a, c
-	ld [wXCoord], a
-	and $1
-	ld [wXBlockCoord], a
-	call LoadMapData              ; reload origin, rendered from the restored pointer
-	and a                         ; carry clear -> back to SL0P menu
+	ld a, [wSlopNoclip]
+	xor $01
+	ld [wSlopNoclip], a
+	scf                            ; carry set -> close menu, back to overworld
 	ret
 
 ; ===========================================================================
diff --git a/home/overworld.asm b/home/overworld.asm
index a41a7ba8..95b94646 100644
--- a/home/overworld.asm
+++ b/home/overworld.asm
@@ -1218,6 +1218,9 @@ SignLoop::
 ; function to check if the player will jump down a ledge and check if the tile ahead is passable (when not surfing)
 ; sets the carry flag if there is a collision, and unsets it if there isn't a collision
 CollisionCheckOnLand::
+	ld a, [wSlopNoclip] ; SL0P noclip: walk through everything (carry clear)
+	and a
+	ret nz
 	ld a, [wMovementFlags]
 	bit BIT_LEDGE_OR_FISHING, a
 	jr nz, .noCollision
@@ -1797,10 +1800,8 @@ LoadPlayerSpriteGraphicsCommon::
 ; function to load data from the map header
 LoadMapHeader::
 	farcall MarkTownVisitedAndLoadToggleableObjects
-	jr asm_0dbd
-
-Func_0db5:: ; unreferenced
-	farcall LoadToggleableObjectData
+; SL0P: removed unreferenced Func_0db5 (farcall LoadToggleableObjectData) to make
+; room in ROM0 for the noclip hook in CollisionCheckOnLand.
 asm_0dbd:
 	ld a, [wCurMapTileset]
 	ld [wUnusedCurMapTilesetCopy], a
diff --git a/ram/wram.asm b/ram/wram.asm
index 62ef1c44..e0488e62 100644
--- a/ram/wram.asm
+++ b/ram/wram.asm
@@ -1943,7 +1943,7 @@ wOptions:: db
 
 wObtainedBadges:: flag_array NUM_BADGES
 
-wUnusedObtainedBadges:: db
+wSlopNoclip:: db ; SL0P: nonzero = noclip free-roam (walk through walls)
 
 wLetterPrintingDelayFlags:: db