10 files changed, 1209 insertions, 0 deletions

diff --git a/engine/overworld/clear_variables.asm b/engine/overworld/clear_variables.asm
new file mode 100644
index 00000000..9a59cc7c
--- /dev/null
+++ b/engine/overworld/clear_variables.asm
@@ -0,0 +1,20 @@
+ClearVariablesOnEnterMap:
+	ld a, SCREEN_HEIGHT_PIXELS
+	ld [hWY], a
+	ld [rWY], a
+	xor a
+	ld [H_AUTOBGTRANSFERENABLED], a
+	ld [wStepCounter], a
+	ld [wLoneAttackNo], a
+	ld [hJoyPressed], a
+	ld [hJoyReleased], a
+	ld [hJoyHeld], a
+	ld [wActionResultOrTookBattleTurn], a
+	ld [wUnusedD5A3], a
+	ld hl, wCardKeyDoorY
+	ld [hli], a
+	ld [hl], a
+	ld hl, wWhichTrade
+	ld bc, wStandingOnWarpPadOrHole - wWhichTrade
+	call FillMemory
+	ret
diff --git a/engine/overworld/daycare_exp.asm b/engine/overworld/daycare_exp.asm
new file mode 100644
index 00000000..dbe4023a
--- /dev/null
+++ b/engine/overworld/daycare_exp.asm
@@ -0,0 +1,18 @@
+IncrementDayCareMonExp:
+	ld a, [wDayCareInUse]
+	and a
+	ret z
+	ld hl, wDayCareMonExp + 2
+	inc [hl]
+	ret nz
+	dec hl
+	inc [hl]
+	ret nz
+	dec hl
+	inc [hl]
+	ld a, [hl]
+	cp $50
+	ret c
+	ld a, $50
+	ld [hl], a
+	ret
diff --git a/engine/overworld/field_move_messages.asm b/engine/overworld/field_move_messages.asm
new file mode 100644
index 00000000..69914bfc
--- /dev/null
+++ b/engine/overworld/field_move_messages.asm
@@ -0,0 +1,57 @@
+PrintStrengthTxt:
+	ld hl, wd728
+	set 0, [hl]
+	ld hl, UsedStrengthText
+	call PrintText
+	ld hl, CanMoveBouldersText
+	jp PrintText
+
+UsedStrengthText:
+	TX_FAR _UsedStrengthText
+	TX_ASM
+	ld a, [wcf91]
+	call PlayCry
+	call Delay3
+	jp TextScriptEnd
+
+CanMoveBouldersText:
+	TX_FAR _CanMoveBouldersText
+	db "@"
+
+IsSurfingAllowed:
+; Returns whether surfing is allowed in bit 1 of wd728.
+; Surfing isn't allowed on the Cycling Road or in the lowest level of the
+; Seafoam Islands before the current has been slowed with boulders.
+	ld hl, wd728
+	set 1, [hl]
+	ld a, [wd732]
+	bit 5, a
+	jr nz, .forcedToRideBike
+	ld a, [wCurMap]
+	cp SEAFOAM_ISLANDS_5
+	ret nz
+	CheckBothEventsSet EVENT_SEAFOAM4_BOULDER1_DOWN_HOLE, EVENT_SEAFOAM4_BOULDER2_DOWN_HOLE
+	ret z
+	ld hl, CoordsData_cdf7
+	call ArePlayerCoordsInArray
+	ret nc
+	ld hl, wd728
+	res 1, [hl]
+	ld hl, CurrentTooFastText
+	jp PrintText
+.forcedToRideBike
+	ld hl, wd728
+	res 1, [hl]
+	ld hl, CyclingIsFunText
+	jp PrintText
+
+CoordsData_cdf7:
+	db $0B,$07,$FF
+
+CurrentTooFastText:
+	TX_FAR _CurrentTooFastText
+	db "@"
+
+CyclingIsFunText:
+	TX_FAR _CyclingIsFunText
+	db "@"
diff --git a/engine/overworld/missable_objects.asm b/engine/overworld/missable_objects.asm
new file mode 100644
index 00000000..8587c0f7
--- /dev/null
+++ b/engine/overworld/missable_objects.asm
@@ -0,0 +1,215 @@
+MarkTownVisitedAndLoadMissableObjects:
+	ld a, [wCurMap]
+	cp ROUTE_1
+	jr nc, .notInTown
+	ld c, a
+	ld b, FLAG_SET
+	ld hl, wTownVisitedFlag   ; mark town as visited (for flying)
+	predef FlagActionPredef
+.notInTown
+	ld hl, MapHSPointers
+	ld a, [wCurMap]
+	ld b, $0
+	ld c, a
+	add hl, bc
+	add hl, bc
+	ld a, [hli]                ; load missable objects pointer in hl
+	ld h, [hl]
+	; fall through
+
+LoadMissableObjects:
+	ld l, a
+	push hl
+	ld de, MapHS00             ; calculate difference between out pointer and the base pointer
+	ld a, l
+	sub e
+	jr nc, .asm_f13c
+	dec h
+.asm_f13c
+	ld l, a
+	ld a, h
+	sub d
+	ld h, a
+	ld a, h
+	ld [H_DIVIDEND], a
+	ld a, l
+	ld [H_DIVIDEND+1], a
+	xor a
+	ld [H_DIVIDEND+2], a
+	ld [H_DIVIDEND+3], a
+	ld a, $3
+	ld [H_DIVISOR], a
+	ld b, $2
+	call Divide                ; divide difference by 3, resulting in the global offset (number of missable items before ours)
+	ld a, [wCurMap]
+	ld b, a
+	ld a, [H_DIVIDEND+3]
+	ld c, a                    ; store global offset in c
+	ld de, wMissableObjectList
+	pop hl
+.writeMissableObjectsListLoop
+	ld a, [hli]
+	cp $ff
+	jr z, .done     ; end of list
+	cp b
+	jr nz, .done    ; not for current map anymore
+	ld a, [hli]
+	inc hl
+	ld [de], a                 ; write (map-local) sprite ID
+	inc de
+	ld a, c
+	inc c
+	ld [de], a                 ; write (global) missable object index
+	inc de
+	jr .writeMissableObjectsListLoop
+.done
+	ld a, $ff
+	ld [de], a                 ; write sentinel
+	ret
+
+InitializeMissableObjectsFlags:
+	ld hl, wMissableObjectFlags
+	ld bc, wMissableObjectFlagsEnd - wMissableObjectFlags
+	xor a
+	call FillMemory ; clear missable objects flags
+	ld hl, MapHS00
+	xor a
+	ld [wMissableObjectCounter], a
+.missableObjectsLoop
+	ld a, [hli]
+	cp $ff          ; end of list
+	ret z
+	push hl
+	inc hl
+	ld a, [hl]
+	cp Hide
+	jr nz, .skip
+	ld hl, wMissableObjectFlags
+	ld a, [wMissableObjectCounter]
+	ld c, a
+	ld b, FLAG_SET
+	call MissableObjectFlagAction ; set flag if Item is hidden
+.skip
+	ld hl, wMissableObjectCounter
+	inc [hl]
+	pop hl
+	inc hl
+	inc hl
+	jr .missableObjectsLoop
+
+; tests if current sprite is a missable object that is hidden/has been removed
+IsObjectHidden:
+	ld a, [H_CURRENTSPRITEOFFSET]
+	swap a
+	ld b, a
+	ld hl, wMissableObjectList
+.loop
+	ld a, [hli]
+	cp $ff
+	jr z, .notHidden ; not missable -> not hidden
+	cp b
+	ld a, [hli]
+	jr nz, .loop
+	ld c, a
+	ld b, FLAG_TEST
+	ld hl, wMissableObjectFlags
+	call MissableObjectFlagAction
+	ld a, c
+	and a
+	jr nz, .hidden
+.notHidden
+	xor a
+.hidden
+	ld [$ffe5], a
+	ret
+
+; adds missable object (items, leg. pokemon, etc.) to the map
+; [wMissableObjectIndex]: index of the missable object to be added (global index)
+ShowObject:
+ShowObject2:
+	ld hl, wMissableObjectFlags
+	ld a, [wMissableObjectIndex]
+	ld c, a
+	ld b, FLAG_RESET
+	call MissableObjectFlagAction   ; reset "removed" flag
+	jp UpdateSprites
+
+; removes missable object (items, leg. pokemon, etc.) from the map
+; [wMissableObjectIndex]: index of the missable object to be removed (global index)
+HideObject:
+	ld hl, wMissableObjectFlags
+	ld a, [wMissableObjectIndex]
+	ld c, a
+	ld b, FLAG_SET
+	call MissableObjectFlagAction   ; set "removed" flag
+	jp UpdateSprites
+
+MissableObjectFlagAction:
+; identical to FlagAction
+
+	push hl
+	push de
+	push bc
+
+	; bit
+	ld a, c
+	ld d, a
+	and 7
+	ld e, a
+
+	; byte
+	ld a, d
+	srl a
+	srl a
+	srl a
+	add l
+	ld l, a
+	jr nc, .ok
+	inc h
+.ok
+
+	; d = 1 << e (bitmask)
+	inc e
+	ld d, 1
+.shift
+	dec e
+	jr z, .shifted
+	sla d
+	jr .shift
+.shifted
+
+	ld a, b
+	and a
+	jr z, .reset
+	cp 2
+	jr z, .read
+
+.set
+	ld a, [hl]
+	ld b, a
+	ld a, d
+	or b
+	ld [hl], a
+	jr .done
+
+.reset
+	ld a, [hl]
+	ld b, a
+	ld a, d
+	xor $ff
+	and b
+	ld [hl], a
+	jr .done
+
+.read
+	ld a, [hl]
+	ld b, a
+	ld a, d
+	and b
+
+.done
+	pop bc
+	pop de
+	pop hl
+	ld c, a
+	ret
diff --git a/engine/overworld/player_state.asm b/engine/overworld/player_state.asm
new file mode 100644
index 00000000..79f755b9
--- /dev/null
+++ b/engine/overworld/player_state.asm
@@ -0,0 +1,463 @@
+; only used for setting bit 2 of wd736 upon entering a new map
+IsPlayerStandingOnWarp:
+	ld a, [wNumberOfWarps]
+	and a
+	ret z
+	ld c, a
+	ld hl, wWarpEntries
+.loop
+	ld a, [wYCoord]
+	cp [hl]
+	jr nz, .nextWarp1
+	inc hl
+	ld a, [wXCoord]
+	cp [hl]
+	jr nz, .nextWarp2
+	inc hl
+	ld a, [hli] ; target warp
+	ld [wDestinationWarpID], a
+	ld a, [hl] ; target map
+	ld [hWarpDestinationMap], a
+	ld hl, wd736
+	set 2, [hl] ; standing on warp flag
+	ret
+.nextWarp1
+	inc hl
+.nextWarp2
+	inc hl
+	inc hl
+	inc hl
+	dec c
+	jr nz, .loop
+	ret
+
+CheckForceBikeOrSurf:
+	ld hl, wd732
+	bit 5, [hl]
+	ret nz
+	ld hl, ForcedBikeOrSurfMaps
+	ld a, [wYCoord]
+	ld b, a
+	ld a, [wXCoord]
+	ld c, a
+	ld a, [wCurMap]
+	ld d, a
+.loop
+	ld a, [hli]
+	cp $ff
+	ret z ;if we reach FF then it's not part of the list
+	cp d ;compare to current map
+	jr nz, .incorrectMap
+	ld a, [hli]
+	cp b ;compare y-coord
+	jr nz, .incorrectY
+	ld a, [hli]
+	cp c ;compare x-coord
+	jr nz, .loop ; incorrect x-coord, check next item
+	ld a, [wCurMap]
+	cp SEAFOAM_ISLANDS_4
+	ld a, $2
+	ld [wSeafoamIslands4CurScript], a
+	jr z, .forceSurfing
+	ld a, [wCurMap]
+	cp SEAFOAM_ISLANDS_5
+	ld a, $2
+	ld [wSeafoamIslands5CurScript], a
+	jr z, .forceSurfing
+	;force bike riding
+	ld hl, wd732
+	set 5, [hl]
+	ld a, $1
+	ld [wWalkBikeSurfState], a
+	ld [wWalkBikeSurfStateCopy], a
+	jp ForceBikeOrSurf
+.incorrectMap
+	inc hl
+.incorrectY
+	inc hl
+	jr .loop
+.forceSurfing
+	ld a, $2
+	ld [wWalkBikeSurfState], a
+	ld [wWalkBikeSurfStateCopy], a
+	jp ForceBikeOrSurf
+
+INCLUDE "data/force_bike_surf.asm"
+
+IsPlayerFacingEdgeOfMap:
+	push hl
+	push de
+	push bc
+	ld a, [wSpriteStateData1 + 9] ; player sprite's facing direction
+	srl a
+	ld c, a
+	ld b, $0
+	ld hl, .functionPointerTable
+	add hl, bc
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	ld a, [wYCoord]
+	ld b, a
+	ld a, [wXCoord]
+	ld c, a
+	ld de, .asm_c41e
+	push de
+	jp [hl]
+.asm_c41e
+	pop bc
+	pop de
+	pop hl
+	ret
+
+.functionPointerTable
+	dw .facingDown
+	dw .facingUp
+	dw .facingLeft
+	dw .facingRight
+
+.facingDown
+	ld a, [wCurMapHeight]
+	add a
+	dec a
+	cp b
+	jr z, .setCarry
+	jr .resetCarry
+
+.facingUp
+	ld a, b
+	and a
+	jr z, .setCarry
+	jr .resetCarry
+
+.facingLeft
+	ld a, c
+	and a
+	jr z, .setCarry
+	jr .resetCarry
+
+.facingRight
+	ld a, [wCurMapWidth]
+	add a
+	dec a
+	cp c
+	jr z, .setCarry
+	jr .resetCarry
+.resetCarry
+	and a
+	ret
+.setCarry
+	scf
+	ret
+
+IsWarpTileInFrontOfPlayer:
+	push hl
+	push de
+	push bc
+	call _GetTileAndCoordsInFrontOfPlayer
+	ld a, [wCurMap]
+	cp SS_ANNE_5
+	jr z, .ssAnne5
+	ld a, [wSpriteStateData1 + 9] ; player sprite's facing direction
+	srl a
+	ld c, a
+	ld b, 0
+	ld hl, .warpTileListPointers
+	add hl, bc
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	ld a, [wTileInFrontOfPlayer]
+	ld de, $1
+	call IsInArray
+.done
+	pop bc
+	pop de
+	pop hl
+	ret
+
+.warpTileListPointers:
+	dw .facingDownWarpTiles
+	dw .facingUpWarpTiles
+	dw .facingLeftWarpTiles
+	dw .facingRightWarpTiles
+
+.facingDownWarpTiles
+	db $01,$12,$17,$3D,$04,$18,$33,$FF
+
+.facingUpWarpTiles
+	db $01,$5C,$FF
+
+.facingLeftWarpTiles
+	db $1A,$4B,$FF
+
+.facingRightWarpTiles
+	db $0F,$4E,$FF
+
+.ssAnne5
+	ld a, [wTileInFrontOfPlayer]
+	cp $15
+	jr nz, .notSSAnne5Warp
+	scf
+	jr .done
+.notSSAnne5Warp
+	and a
+	jr .done
+
+IsPlayerStandingOnDoorTileOrWarpTile:
+	push hl
+	push de
+	push bc
+	callba IsPlayerStandingOnDoorTile
+	jr c, .done
+	ld a, [wCurMapTileset]
+	add a
+	ld c, a
+	ld b, $0
+	ld hl, WarpTileIDPointers
+	add hl, bc
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	ld de, $1
+	aCoord 8, 9
+	call IsInArray
+	jr nc, .done
+	ld hl, wd736
+	res 2, [hl]
+.done
+	pop bc
+	pop de
+	pop hl
+	ret
+
+INCLUDE "data/warp_tile_ids.asm"
+
+PrintSafariZoneSteps:
+	ld a, [wCurMap]
+	cp SAFARI_ZONE_EAST
+	ret c
+	cp UNKNOWN_DUNGEON_2
+	ret nc
+	coord hl, 0, 0
+	ld b, 3
+	ld c, 7
+	call TextBoxBorder
+	coord hl, 1, 1
+	ld de, wSafariSteps
+	lb bc, 2, 3
+	call PrintNumber
+	coord hl, 4, 1
+	ld de, SafariSteps
+	call PlaceString
+	coord hl, 1, 3
+	ld de, SafariBallText
+	call PlaceString
+	ld a, [wNumSafariBalls]
+	cp 10
+	jr nc, .asm_c56d
+	coord hl, 5, 3
+	ld a, " "
+	ld [hl], a
+.asm_c56d
+	coord hl, 6, 3
+	ld de, wNumSafariBalls
+	lb bc, 1, 2
+	jp PrintNumber
+
+SafariSteps:
+	db "/500@"
+
+SafariBallText:
+	db "BALL×× @"
+
+GetTileAndCoordsInFrontOfPlayer:
+	call GetPredefRegisters
+
+_GetTileAndCoordsInFrontOfPlayer:
+	ld a, [wYCoord]
+	ld d, a
+	ld a, [wXCoord]
+	ld e, a
+	ld a, [wSpriteStateData1 + 9] ; player's sprite facing direction
+	and a ; cp SPRITE_FACING_DOWN
+	jr nz, .notFacingDown
+; facing down
+	aCoord 8, 11
+	inc d
+	jr .storeTile
+.notFacingDown
+	cp SPRITE_FACING_UP
+	jr nz, .notFacingUp
+; facing up
+	aCoord 8, 7
+	dec d
+	jr .storeTile
+.notFacingUp
+	cp SPRITE_FACING_LEFT
+	jr nz, .notFacingLeft
+; facing left
+	aCoord 6, 9
+	dec e
+	jr .storeTile
+.notFacingLeft
+	cp SPRITE_FACING_RIGHT
+	jr nz, .storeTile
+; facing right
+	aCoord 10, 9
+	inc e
+.storeTile
+	ld c, a
+	ld [wTileInFrontOfPlayer], a
+	ret
+
+GetTileTwoStepsInFrontOfPlayer:
+	xor a
+	ld [$ffdb], a
+	ld hl, wYCoord
+	ld a, [hli]
+	ld d, a
+	ld e, [hl]
+	ld a, [wSpriteStateData1 + 9] ; player's sprite facing direction
+	and a ; cp SPRITE_FACING_DOWN
+	jr nz, .notFacingDown
+; facing down
+	ld hl, $ffdb
+	set 0, [hl]
+	aCoord 8, 13
+	inc d
+	jr .storeTile
+.notFacingDown
+	cp SPRITE_FACING_UP
+	jr nz, .notFacingUp
+; facing up
+	ld hl, $ffdb
+	set 1, [hl]
+	aCoord 8, 5
+	dec d
+	jr .storeTile
+.notFacingUp
+	cp SPRITE_FACING_LEFT
+	jr nz, .notFacingLeft
+; facing left
+	ld hl, $ffdb
+	set 2, [hl]
+	aCoord 4, 9
+	dec e
+	jr .storeTile
+.notFacingLeft
+	cp SPRITE_FACING_RIGHT
+	jr nz, .storeTile
+; facing right
+	ld hl, $ffdb
+	set 3, [hl]
+	aCoord 12, 9
+	inc e
+.storeTile
+	ld c, a
+	ld [wTileInFrontOfBoulderAndBoulderCollisionResult], a
+	ld [wTileInFrontOfPlayer], a
+	ret
+
+CheckForCollisionWhenPushingBoulder:
+	call GetTileTwoStepsInFrontOfPlayer
+	ld hl, wTilesetCollisionPtr
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+.loop
+	ld a, [hli]
+	cp $ff
+	jr z, .done ; if the tile two steps ahead is not passable
+	cp c
+	jr nz, .loop
+	ld hl, TilePairCollisionsLand
+	call CheckForTilePairCollisions2
+	ld a, $ff
+	jr c, .done ; if there is an elevation difference between the current tile and the one two steps ahead
+	ld a, [wTileInFrontOfBoulderAndBoulderCollisionResult]
+	cp $15 ; stairs tile
+	ld a, $ff
+	jr z, .done ; if the tile two steps ahead is stairs
+	call CheckForBoulderCollisionWithSprites
+.done
+	ld [wTileInFrontOfBoulderAndBoulderCollisionResult], a
+	ret
+
+; sets a to $ff if there is a collision and $00 if there is no collision
+CheckForBoulderCollisionWithSprites:
+	ld a, [wBoulderSpriteIndex]
+	dec a
+	swap a
+	ld d, 0
+	ld e, a
+	ld hl, wSpriteStateData2 + $14
+	add hl, de
+	ld a, [hli] ; map Y position
+	ld [$ffdc], a
+	ld a, [hl] ; map X position
+	ld [$ffdd], a
+	ld a, [wNumSprites]
+	ld c, a
+	ld de, $f
+	ld hl, wSpriteStateData2 + $14
+	ld a, [$ffdb]
+	and $3 ; facing up or down?
+	jr z, .pushingHorizontallyLoop
+.pushingVerticallyLoop
+	inc hl
+	ld a, [$ffdd]
+	cp [hl]
+	jr nz, .nextSprite1 ; if X coordinates don't match
+	dec hl
+	ld a, [hli]
+	ld b, a
+	ld a, [$ffdb]
+	rrca
+	jr c, .pushingDown
+; pushing up
+	ld a, [$ffdc]
+	dec a
+	jr .compareYCoords
+.pushingDown
+	ld a, [$ffdc]
+	inc a
+.compareYCoords
+	cp b
+	jr z, .failure
+.nextSprite1
+	dec c
+	jr z, .success
+	add hl, de
+	jr .pushingVerticallyLoop
+.pushingHorizontallyLoop
+	ld a, [hli]
+	ld b, a
+	ld a, [$ffdc]
+	cp b
+	jr nz, .nextSprite2
+	ld b, [hl]
+	ld a, [$ffdb]
+	bit 2, a
+	jr nz, .pushingLeft
+; pushing right
+	ld a, [$ffdd]
+	inc a
+	jr .compareXCoords
+.pushingLeft
+	ld a, [$ffdd]
+	dec a
+.compareXCoords
+	cp b
+	jr z, .failure
+.nextSprite2
+	dec c
+	jr z, .success
+	add hl, de
+	jr .pushingHorizontallyLoop
+.failure
+	ld a, $ff
+	ret
+.success
+	xor a
+	ret
diff --git a/engine/overworld/poison.asm b/engine/overworld/poison.asm
new file mode 100644
index 00000000..75f68568
--- /dev/null
+++ b/engine/overworld/poison.asm
@@ -0,0 +1,112 @@
+ApplyOutOfBattlePoisonDamage:
+	ld a, [wd730]
+	add a
+	jp c, .noBlackOut ; no black out if joypad states are being simulated
+	ld a, [wPartyCount]
+	and a
+	jp z, .noBlackOut
+	call IncrementDayCareMonExp
+	ld a, [wStepCounter]
+	and $3 ; is the counter a multiple of 4?
+	jp nz, .noBlackOut ; only apply poison damage every fourth step
+	ld [wWhichPokemon], a
+	ld hl, wPartyMon1Status
+	ld de, wPartySpecies
+.applyDamageLoop
+	ld a, [hl]
+	and (1 << PSN)
+	jr z, .nextMon2 ; not poisoned
+	dec hl
+	dec hl
+	ld a, [hld]
+	ld b, a
+	ld a, [hli]
+	or b
+	jr z, .nextMon ; already fainted
+; subtract 1 from HP
+	ld a, [hl]
+	dec a
+	ld [hld], a
+	inc a
+	jr nz, .noBorrow
+; borrow 1 from upper byte of HP
+	dec [hl]
+	inc hl
+	jr .nextMon
+.noBorrow
+	ld a, [hli]
+	or [hl]
+	jr nz, .nextMon ; didn't faint from damage
+; the mon fainted from the damage
+	push hl
+	inc hl
+	inc hl
+	ld [hl], a
+	ld a, [de]
+	ld [wd11e], a
+	push de
+	ld a, [wWhichPokemon]
+	ld hl, wPartyMonNicks
+	call GetPartyMonName
+	xor a
+	ld [wJoyIgnore], a
+	call EnableAutoTextBoxDrawing
+	ld a, $d0
+	ld [hSpriteIndexOrTextID], a
+	call DisplayTextID
+	pop de
+	pop hl
+.nextMon
+	inc hl
+	inc hl
+.nextMon2
+	inc de
+	ld a, [de]
+	inc a
+	jr z, .applyDamageLoopDone
+	ld bc, wPartyMon2 - wPartyMon1
+	add hl, bc
+	push hl
+	ld hl, wWhichPokemon
+	inc [hl]
+	pop hl
+	jr .applyDamageLoop
+.applyDamageLoopDone
+	ld hl, wPartyMon1Status
+	ld a, [wPartyCount]
+	ld d, a
+	ld e, 0
+.countPoisonedLoop
+	ld a, [hl]
+	and (1 << PSN)
+	or e
+	ld e, a
+	ld bc, wPartyMon2 - wPartyMon1
+	add hl, bc
+	dec d
+	jr nz, .countPoisonedLoop
+	ld a, e
+	and a ; are any party members poisoned?
+	jr z, .skipPoisonEffectAndSound
+	ld b, $2
+	predef ChangeBGPalColor0_4Frames ; change BG white to dark grey for 4 frames
+	ld a, SFX_POISONED
+	call PlaySound
+.skipPoisonEffectAndSound
+	predef AnyPartyAlive
+	ld a, d
+	and a
+	jr nz, .noBlackOut
+	call EnableAutoTextBoxDrawing
+	ld a, $d1
+	ld [hSpriteIndexOrTextID], a
+	call DisplayTextID
+	ld hl, wd72e
+	set 5, [hl]
+	ld a, $ff
+	jr .done
+.noBlackOut
+	xor a
+.done
+	ld [wOutOfBattleBlackout], a
+	ret
diff --git a/engine/overworld/push_boulder.asm b/engine/overworld/push_boulder.asm
new file mode 100644
index 00000000..c91605a8
--- /dev/null
+++ b/engine/overworld/push_boulder.asm
@@ -0,0 +1,105 @@
+TryPushingBoulder:
+	ld a, [wd728]
+	bit 0, a ; using Strength?
+	ret z
+	ld a, [wFlags_0xcd60]
+	bit 1, a ; has boulder dust animation from previous push played yet?
+	ret nz
+	xor a
+	ld [hSpriteIndexOrTextID], a
+	call IsSpriteInFrontOfPlayer
+	ld a, [hSpriteIndexOrTextID]
+	ld [wBoulderSpriteIndex], a
+	and a
+	jp z, ResetBoulderPushFlags
+	ld hl, wSpriteStateData1 + 1
+	ld d, $0
+	ld a, [hSpriteIndexOrTextID]
+	swap a
+	ld e, a
+	add hl, de
+	res 7, [hl]
+	call GetSpriteMovementByte2Pointer
+	ld a, [hl]
+	cp BOULDER_MOVEMENT_BYTE_2
+	jp nz, ResetBoulderPushFlags
+	ld hl, wFlags_0xcd60
+	bit 6, [hl]
+	set 6, [hl] ; indicate that the player has tried pushing
+	ret z ; the player must try pushing twice before the boulder will move
+	ld a, [hJoyHeld]
+	and D_RIGHT | D_LEFT | D_UP | D_DOWN
+	ret z
+	predef CheckForCollisionWhenPushingBoulder
+	ld a, [wTileInFrontOfBoulderAndBoulderCollisionResult]
+	and a ; was there a collision?
+	jp nz, ResetBoulderPushFlags
+	ld a, [hJoyHeld]
+	ld b, a
+	ld a, [wSpriteStateData1 + 9] ; player's sprite facing direction
+	cp SPRITE_FACING_UP
+	jr z, .pushBoulderUp
+	cp SPRITE_FACING_LEFT
+	jr z, .pushBoulderLeft
+	cp SPRITE_FACING_RIGHT
+	jr z, .pushBoulderRight
+.pushBoulderDown
+	bit 7, b
+	ret z
+	ld de, PushBoulderDownMovementData
+	jr .done
+.pushBoulderUp
+	bit 6, b
+	ret z
+	ld de, PushBoulderUpMovementData
+	jr .done
+.pushBoulderLeft
+	bit 5, b
+	ret z
+	ld de, PushBoulderLeftMovementData
+	jr .done
+.pushBoulderRight
+	bit 4, b
+	ret z
+	ld de, PushBoulderRightMovementData
+.done
+	call MoveSprite
+	ld a, SFX_PUSH_BOULDER
+	call PlaySound
+	ld hl, wFlags_0xcd60
+	set 1, [hl]
+	ret
+
+PushBoulderUpMovementData:
+	db NPC_MOVEMENT_UP,$FF
+
+PushBoulderDownMovementData:
+	db NPC_MOVEMENT_DOWN,$FF
+
+PushBoulderLeftMovementData:
+	db NPC_MOVEMENT_LEFT,$FF
+
+PushBoulderRightMovementData:
+	db NPC_MOVEMENT_RIGHT,$FF
+
+DoBoulderDustAnimation:
+	ld a, [wd730]
+	bit 0, a
+	ret nz
+	callab AnimateBoulderDust
+	call DiscardButtonPresses
+	ld [wJoyIgnore], a
+	call ResetBoulderPushFlags
+	set 7, [hl]
+	ld a, [wBoulderSpriteIndex]
+	ld [H_SPRITEINDEX], a
+	call GetSpriteMovementByte2Pointer
+	ld [hl], $10
+	ld a, SFX_CUT
+	jp PlaySound
+
+ResetBoulderPushFlags:
+	ld hl, wFlags_0xcd60
+	res 1, [hl]
+	res 6, [hl]
+	ret
diff --git a/engine/overworld/tileset_header.asm b/engine/overworld/tileset_header.asm
new file mode 100644
index 00000000..6e33974f
--- /dev/null
+++ b/engine/overworld/tileset_header.asm
@@ -0,0 +1,60 @@
+LoadTilesetHeader:
+	call GetPredefRegisters
+	push hl
+	ld d, 0
+	ld a, [wCurMapTileset]
+	add a
+	add a
+	ld b, a
+	add a
+	add b ; a = tileset * 12
+	jr nc, .noCarry
+	inc d
+.noCarry
+	ld e, a
+	ld hl, Tilesets
+	add hl, de
+	ld de, wTilesetBank
+	ld c, $b
+.copyTilesetHeaderLoop
+	ld a, [hli]
+	ld [de], a
+	inc de
+	dec c
+	jr nz, .copyTilesetHeaderLoop
+	ld a, [hl]
+	ld [hTilesetType], a
+	xor a
+	ld [$ffd8], a
+	pop hl
+	ld a, [wCurMapTileset]
+	push hl
+	push de
+	ld hl, DungeonTilesets
+	ld de, $1
+	call IsInArray
+	pop de
+	pop hl
+	jr c, .asm_c797
+	ld a, [wCurMapTileset]
+	ld b, a
+	ld a, [hPreviousTileset]
+	cp b
+	jr z, .done
+.asm_c797
+	ld a, [wDestinationWarpID]
+	cp $ff
+	jr z, .done
+	call LoadDestinationWarpPosition
+	ld a, [wYCoord]
+	and $1
+	ld [wYBlockCoord], a
+	ld a, [wXCoord]
+	and $1
+	ld [wXBlockCoord], a
+.done
+	ret
+
+INCLUDE "data/dungeon_tilesets.asm"
+
+INCLUDE "data/tileset_headers.asm"
diff --git a/engine/overworld/update_map.asm b/engine/overworld/update_map.asm
new file mode 100644
index 00000000..8577b9e7
--- /dev/null
+++ b/engine/overworld/update_map.asm
@@ -0,0 +1,126 @@
+; replaces a tile block with the one specified in [wNewTileBlockID]
+; and redraws the map view if necessary
+; b = Y
+; c = X
+ReplaceTileBlock:
+	call GetPredefRegisters
+	ld hl, wOverworldMap
+	ld a, [wCurMapWidth]
+	add $6
+	ld e, a
+	ld d, $0
+	add hl, de
+	add hl, de
+	add hl, de
+	ld e, $3
+	add hl, de
+	ld e, a
+	ld a, b
+	and a
+	jr z, .addX
+; add width * Y
+.addWidthYTimesLoop
+	add hl, de
+	dec b
+	jr nz, .addWidthYTimesLoop
+.addX
+	add hl, bc ; add X
+	ld a, [wNewTileBlockID]
+	ld [hl], a
+	ld a, [wCurrentTileBlockMapViewPointer]
+	ld c, a
+	ld a, [wCurrentTileBlockMapViewPointer + 1]
+	ld b, a
+	call CompareHLWithBC
+	ret c ; return if the replaced tile block is below the map view in memory
+	push hl
+	ld l, e
+	ld h, $0
+	ld e, $6
+	ld d, h
+	add hl, hl
+	add hl, hl
+	add hl, de
+	add hl, bc
+	pop bc
+	call CompareHLWithBC
+	ret c ; return if the replaced tile block is above the map view in memory
+
+RedrawMapView:
+	ld a, [wIsInBattle]
+	inc a
+	ret z
+	ld a, [H_AUTOBGTRANSFERENABLED]
+	push af
+	ld a, [hTilesetType]
+	push af
+	xor a
+	ld [H_AUTOBGTRANSFERENABLED], a
+	ld [hTilesetType], a ; no flower/water BG tile animations
+	call LoadCurrentMapView
+	call RunDefaultPaletteCommand
+	ld hl, wMapViewVRAMPointer
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	ld de, -2 * 32
+	add hl, de
+	ld a, h
+	and $3
+	or $98
+	ld a, l
+	ld [wBuffer], a
+	ld a, h
+	ld [wBuffer + 1], a ; this copy of the address is not used
+	ld a, 2
+	ld [$ffbe], a
+	ld c, 9 ; number of rows of 2x2 tiles (this covers the whole screen)
+.redrawRowLoop
+	push bc
+	push hl
+	push hl
+	ld hl, wTileMap - 2 * SCREEN_WIDTH
+	ld de, SCREEN_WIDTH
+	ld a, [$ffbe]
+.calcWRAMAddrLoop
+	add hl, de
+	dec a
+	jr nz, .calcWRAMAddrLoop
+	call CopyToRedrawRowOrColumnSrcTiles
+	pop hl
+	ld de, $20
+	ld a, [$ffbe]
+	ld c, a
+.calcVRAMAddrLoop
+	add hl, de
+	ld a, h
+	and $3
+	or $98
+	dec c
+	jr nz, .calcVRAMAddrLoop
+	ld [hRedrawRowOrColumnDest + 1], a
+	ld a, l
+	ld [hRedrawRowOrColumnDest], a
+	ld a, REDRAW_ROW
+	ld [hRedrawRowOrColumnMode], a
+	call DelayFrame
+	ld hl, $ffbe
+	inc [hl]
+	inc [hl]
+	pop hl
+	pop bc
+	dec c
+	jr nz, .redrawRowLoop
+	pop af
+	ld [hTilesetType], a
+	pop af
+	ld [H_AUTOBGTRANSFERENABLED], a
+	ret
+
+CompareHLWithBC:
+	ld a, h
+	sub b
+	ret nz
+	ld a, l
+	sub c
+	ret
diff --git a/engine/overworld/wild_mons.asm b/engine/overworld/wild_mons.asm
new file mode 100644
index 00000000..6444ab7e
--- /dev/null
+++ b/engine/overworld/wild_mons.asm
@@ -0,0 +1,33 @@
+LoadWildData:
+	ld hl,WildDataPointers
+	ld a,[wCurMap]
+
+	; get wild data for current map
+	ld c,a
+	ld b,0
+	add hl,bc
+	add hl,bc
+	ld a,[hli]
+	ld h,[hl]
+	ld l,a       ; hl now points to wild data for current map
+	ld a,[hli]
+	ld [wGrassRate],a
+	and a
+	jr z,.NoGrassData ; if no grass data, skip to surfing data
+	push hl
+	ld de,wGrassMons ; otherwise, load grass data
+	ld bc,$0014
+	call CopyData
+	pop hl
+	ld bc,$0014
+	add hl,bc
+.NoGrassData
+	ld a,[hli]
+	ld [wWaterRate],a
+	and a
+	ret z        ; if no water data, we're done
+	ld de,wWaterMons  ; otherwise, load surfing data
+	ld bc,$0014
+	jp CopyData
+
+INCLUDE "data/wild_mons.asm"