Use more hardware and graphics constants (#532)

- Use `OBJ_SIZE` and `TILE_SIZE` from hardware.inc.
- `SPRITESTATEDATA1_LENGTH`, `NUM_SPRITESTATEDATA_STRUCTS`
  and `TILE_1BPP_SIZE` are used in some places.
- Highlight an oversight in `OakSpeech` where several
  direct MBC bank switches are requested.
- Remove redundant comments in home/overworld.asm.
- Add unreferenced `FillBgMap` function to avoid a byte
  of dead code.
- Some constants added in wram.asm.
- Correctly separate the commented code in `SaveMainData`.

35 files changed, 138 insertions, 121 deletions

diff --git a/engine/battle/animations.asm b/engine/battle/animations.asm
index 40b2047b..711ebda4 100644
--- a/engine/battle/animations.asm
+++ b/engine/battle/animations.asm
@@ -928,7 +928,7 @@ BallMoveDistances2:
 DoGrowlSpecialEffects:
 	ld hl, wShadowOAM
 	ld de, wShadowOAMSprite04
-	ld bc, $10
+	ld bc, OBJ_SIZE * 4
 	call CopyData ; copy the musical note graphic
 	ld a, [wSubAnimCounter]
 	dec a
@@ -1308,7 +1308,7 @@ AdjustOAMBlockXPos:
 	ld h, d
 
 AdjustOAMBlockXPos2:
-	ld de, 4
+	ld de, OBJ_SIZE
 .loop
 	ld a, [wCoordAdjustmentAmount]
 	ld b, a
@@ -1318,7 +1318,7 @@ AdjustOAMBlockXPos2:
 	jr c, .skipPuttingEntryOffScreen
 ; put off-screen if X >= 168
 	dec hl
-	ld a, 160
+	ld a, SCREEN_HEIGHT_PX + OAM_Y_OFS
 	ld [hli], a
 .skipPuttingEntryOffScreen
 	ld [hl], a
@@ -1332,7 +1332,7 @@ AdjustOAMBlockYPos:
 	ld h, d
 
 AdjustOAMBlockYPos2:
-	ld de, 4
+	ld de, OBJ_SIZE
 .loop
 	ld a, [wCoordAdjustmentAmount]
 	ld b, a
@@ -1670,7 +1670,7 @@ _AnimationShootBallsUpward:
 	dec a
 	ld [wNumShootingBalls], a
 .next
-	ld de, 4
+	ld de, OBJ_SIZE
 	add hl, de ; next OAM entry
 	dec b
 	jr nz, .innerLoop
@@ -1723,10 +1723,10 @@ AnimationMinimizeMon:
 	ld hl, wTempPic
 	push hl
 	xor a
-	ld bc, 7 * 7 * $10
+	ld bc, (7 * 7) tiles
 	call FillMemory
 	pop hl
-	ld de, 7 * 3 * $10 + 4 * $10 + 4
+	ld de, (7 * 3 + 4) tiles + TILE_SIZE / 4
 	add hl, de
 	ld de, MinimizedMonSprite
 	ld c, MinimizedMonSpriteEnd - MinimizedMonSprite
@@ -1971,7 +1971,7 @@ AnimationSubstitute:
 	jp AnimationShowMonPic
 
 CopyMonsterSpriteData:
-	ld bc, 1 tiles
+	ld bc, TILE_SIZE
 	ld a, BANK(MonsterSprite)
 	jp FarCopyData2
 
@@ -2379,7 +2379,7 @@ FallingObjects_UpdateOAMEntry:
 	inc a
 	cp 112
 	jr c, .next
-	ld a, 160 ; if Y >= 112, put it off-screen
+	ld a, SCREEN_HEIGHT_PX + OAM_Y_OFS ; if Y >= 112, put it off-screen
 .next
 	ld [hli], a ; Y
 	ld a, [wFallingObjectMovementByte]
diff --git a/engine/battle/battle_transitions.asm b/engine/battle/battle_transitions.asm
index fe731c5d..3670cddc 100644
--- a/engine/battle/battle_transitions.asm
+++ b/engine/battle/battle_transitions.asm
@@ -14,7 +14,7 @@ BattleTransition:
 	ldh a, [hSpriteIndex] ; enemy trainer sprite index (0 if wild battle)
 	ld c, a
 	ld b, 0
-	ld de, $10
+	ld de, SPRITESTATEDATA1_LENGTH
 .loop1
 	ld a, [hl]
 	cp $ff
@@ -35,13 +35,13 @@ BattleTransition:
 	jr z, .skip2 ; skip clearing the block if the enemy trainer is using it
 	push hl
 	push bc
-	ld bc, $10
+	ld bc, OBJ_SIZE * 4
 	xor a
 	call FillMemory
 	pop bc
 	pop hl
 .skip2
-	ld de, $10
+	ld de, OBJ_SIZE * 4
 	add hl, de
 	dec c
 	jr nz, .loop2
diff --git a/engine/battle/core.asm b/engine/battle/core.asm
index 87abf2e8..0916176c 100644
--- a/engine/battle/core.asm
+++ b/engine/battle/core.asm
@@ -106,8 +106,8 @@ SlidePlayerAndEnemySilhouettesOnScreen:
 SlidePlayerHeadLeft:
 	push bc
 	ld hl, wShadowOAMSprite00XCoord
-	ld c, $15 ; number of OAM entries
-	ld de, $4 ; size of OAM entry
+	ld c, 7 * 3 ; number of OAM entries
+	ld de, OBJ_SIZE
 .loop
 	dec [hl] ; decrement X
 	dec [hl] ; decrement X
@@ -6655,11 +6655,11 @@ LoadHudTilePatterns:
 .lcdEnabled
 	ld de, BattleHudTiles1
 	ld hl, vChars2 tile $6d
-	lb bc, BANK(BattleHudTiles1), (BattleHudTiles1End - BattleHudTiles1) / $8
+	lb bc, BANK(BattleHudTiles1), (BattleHudTiles1End - BattleHudTiles1) / TILE_1BPP_SIZE
 	call CopyVideoDataDouble
 	ld de, BattleHudTiles2
 	ld hl, vChars2 tile $73
-	lb bc, BANK(BattleHudTiles2), (BattleHudTiles3End - BattleHudTiles2) / $8
+	lb bc, BANK(BattleHudTiles2), (BattleHudTiles3End - BattleHudTiles2) / TILE_1BPP_SIZE
 	jp CopyVideoDataDouble
 
 PrintEmptyString:
@@ -7040,14 +7040,14 @@ LoadMonBackPic:
 	ld b, 7
 	ld c, 8
 	call ClearScreenArea
-	ld hl,  wMonHBackSprite - wMonHeader
+	ld hl, wMonHBackSprite - wMonHeader
 	call UncompressMonSprite
 	predef ScaleSpriteByTwo
 	ld de, vBackPic
 	call InterlaceMergeSpriteBuffers ; combine the two buffers to a single 2bpp sprite
 	ld hl, vSprites
 	ld de, vBackPic
-	ld c, (2 * SPRITEBUFFERSIZE) / 16 ; count of 16-byte chunks to be copied
+	ld c, (2 * SPRITEBUFFERSIZE) / TILE_SIZE ; count of 16-byte chunks to be copied
 	ldh a, [hLoadedROMBank]
 	ld b, a
 	jp CopyVideoData
diff --git a/engine/battle/draw_hud_pokeball_gfx.asm b/engine/battle/draw_hud_pokeball_gfx.asm
index 34bff58d..983e7cdf 100644
--- a/engine/battle/draw_hud_pokeball_gfx.asm
+++ b/engine/battle/draw_hud_pokeball_gfx.asm
@@ -13,7 +13,7 @@ DrawEnemyPokeballs:
 LoadPartyPokeballGfx:
 	ld de, PokeballTileGraphics
 	ld hl, vSprites tile $31
-	lb bc, BANK(PokeballTileGraphics), (PokeballTileGraphicsEnd - PokeballTileGraphics) / $10
+	lb bc, BANK(PokeballTileGraphics), (PokeballTileGraphicsEnd - PokeballTileGraphics) / TILE_SIZE
 	jp CopyVideoData
 
 SetupOwnPartyPokeballs:
diff --git a/engine/battle/effects.asm b/engine/battle/effects.asm
index 413c34d9..e107853c 100644
--- a/engine/battle/effects.asm
+++ b/engine/battle/effects.asm
@@ -686,7 +686,7 @@ UpdateLoweredStatDone:
 .ApplyBadgeBoostsAndStatusPenalties
 	ldh a, [hWhoseTurn]
 	and a
-	call nz, ApplyBadgeStatBoosts ; whenever the player uses a stat-down move, badge boosts get reapplied again to every stat,
+	call nz, ApplyBadgeStatBoosts ; whenever the opponent uses a stat-down move, badge boosts get reapplied again to every stat,
 	                              ; even to those not affected by the stat-down move (will be boosted further)
 	ld hl, MonsStatsFellText
 	call PrintText
diff --git a/engine/events/diploma.asm b/engine/events/diploma.asm
index b4ccbb07..3d181210 100644
--- a/engine/events/diploma.asm
+++ b/engine/events/diploma.asm
@@ -11,7 +11,7 @@ DisplayDiploma::
 	call DisableLCD
 	ld hl, CircleTile
 	ld de, vChars2 tile CIRCLE_TILE_ID
-	ld bc, $10
+	ld bc, TILE_SIZE
 	ld a, BANK(CircleTile)
 	call FarCopyData2
 	hlcoord 0, 0
diff --git a/engine/gfx/load_pokedex_tiles.asm b/engine/gfx/load_pokedex_tiles.asm
index a3f69171..b0857137 100644
--- a/engine/gfx/load_pokedex_tiles.asm
+++ b/engine/gfx/load_pokedex_tiles.asm
@@ -3,7 +3,7 @@ LoadPokedexTilePatterns:
 	call LoadHpBarAndStatusTilePatterns
 	ld de, PokedexTileGraphics
 	ld hl, vChars2 tile $60
-	lb bc, BANK(PokedexTileGraphics), (PokedexTileGraphicsEnd - PokedexTileGraphics) / $10
+	lb bc, BANK(PokedexTileGraphics), (PokedexTileGraphicsEnd - PokedexTileGraphics) / TILE_SIZE
 	call CopyVideoData
 	ld de, PokeballTileGraphics
 	ld hl, vChars2 tile $72
diff --git a/engine/gfx/mon_icons.asm b/engine/gfx/mon_icons.asm
index 49e789a5..63da2345 100644
--- a/engine/gfx/mon_icons.asm
+++ b/engine/gfx/mon_icons.asm
@@ -44,7 +44,7 @@ GetAnimationSpeed:
 	push bc
 	ld hl, wMonPartySpritesSavedOAM
 	ld de, wShadowOAM
-	ld bc, $60
+	ld bc, OBJ_SIZE * 4 * PARTY_LENGTH
 	call CopyData
 	pop bc
 	xor a
@@ -52,7 +52,7 @@ GetAnimationSpeed:
 .animateSprite
 	push bc
 	ld hl, wShadowOAMSprite00TileID
-	ld bc, $10
+	ld bc, OBJ_SIZE * 4
 	ld a, [wCurrentMenuItem]
 	call AddNTimes
 	ld c, ICONOFFSET
@@ -68,8 +68,8 @@ GetAnimationSpeed:
 	ld c, $1 ; amount to increase the y coord by
 ; otherwise, load a second sprite frame
 .editTileIDS
-	ld b, $4
-	ld de, $4
+	ld b, 4
+	ld de, OBJ_SIZE
 .loop
 	ld a, [hl]
 	add c
@@ -254,7 +254,7 @@ WriteMonPartySpriteOAM:
 .makeCopy
 	ld hl, wShadowOAM
 	ld de, wMonPartySpritesSavedOAM
-	ld bc, $60
+	ld bc, OBJ_SIZE * 4 * PARTY_LENGTH
 	jp CopyData
 
 GetPartyMonSpriteID:
diff --git a/engine/gfx/palettes.asm b/engine/gfx/palettes.asm
index 0497f74a..f4ae5c39 100644
--- a/engine/gfx/palettes.asm
+++ b/engine/gfx/palettes.asm
@@ -611,7 +611,7 @@ CopySGBBorderTiles:
 	ld b, 128
 .tileLoop
 ; Copy bit planes 1 and 2 of the tile data.
-	ld c, 16
+	ld c, TILE_SIZE
 .copyLoop
 	ld a, [hli]
 	ld [de], a
diff --git a/engine/gfx/sprite_oam.asm b/engine/gfx/sprite_oam.asm
index 737443a6..649ab01e 100644
--- a/engine/gfx/sprite_oam.asm
+++ b/engine/gfx/sprite_oam.asm
@@ -148,16 +148,16 @@ PrepareOAMData::
 	ldh a, [hOAMBufferOffset]
 	ld l, a
 	ld h, HIGH(wShadowOAM)
-	ld de, $4
-	ld b, $a0
+	ld de, OBJ_SIZE
+	ld b, SCREEN_HEIGHT_PX + OAM_Y_OFS
 	ld a, [wMovementFlags]
 	bit BIT_LEDGE_OR_FISHING, a
-	ld a, $a0
+	ld a, LOW(wShadowOAMEnd)
 	jr z, .clear
 
 ; Don't clear the last 4 entries because they are used for the shadow in the
 ; jumping down ledge animation and the rod in the fishing animation.
-	ld a, $90
+	ld a, LOW(wShadowOAMSprite36)
 
 .clear
 	cp l
diff --git a/engine/items/town_map.asm b/engine/items/town_map.asm
index 6758adea..573ba581 100644
--- a/engine/items/town_map.asm
+++ b/engine/items/town_map.asm
@@ -24,7 +24,7 @@ DisplayTownMap:
 	call CopyData
 	ld hl, vSprites tile BIRD_BASE_TILE
 	ld de, TownMapCursor
-	lb bc, BANK(TownMapCursor), (TownMapCursorEnd - TownMapCursor) / $8
+	lb bc, BANK(TownMapCursor), (TownMapCursorEnd - TownMapCursor) / TILE_1BPP_SIZE
 	call CopyVideoDataDouble
 	xor a
 	ld [wWhichTownMapLocation], a
@@ -149,7 +149,7 @@ LoadTownMap_Fly::
 	call CopyVideoData
 	ld de, TownMapUpArrow
 	ld hl, vChars1 tile $6d
-	lb bc, BANK(TownMapUpArrow), (TownMapUpArrowEnd - TownMapUpArrow) / $8
+	lb bc, BANK(TownMapUpArrow), (TownMapUpArrowEnd - TownMapUpArrow) / TILE_1BPP_SIZE
 	call CopyVideoDataDouble
 	call BuildFlyLocationsList
 	ld hl, wUpdateSpritesEnabled
@@ -609,11 +609,11 @@ TownMapSpriteBlinkingAnimation::
 	xor a
 	jr .done
 .hideSprites
-	ld hl, wShadowOAM
+	ld hl, wShadowOAMSprite00YCoord
 	ld b, OAM_COUNT - 4
-	ld de, $4
+	ld de, OBJ_SIZE
 .hideSpritesLoop
-	ld [hl], $a0
+	ld [hl], SCREEN_HEIGHT_PX + OAM_Y_OFS
 	add hl, de
 	dec b
 	jr nz, .hideSpritesLoop
diff --git a/engine/link/cable_club.asm b/engine/link/cable_club.asm
index c94b2693..ea39b938 100644
--- a/engine/link/cable_club.asm
+++ b/engine/link/cable_club.asm
@@ -977,5 +977,5 @@ CableClub_DrawHorizontalLine:
 LoadTrainerInfoTextBoxTiles:
 	ld de, TrainerInfoTextBoxTileGraphics
 	ld hl, vChars2 tile $76
-	lb bc, BANK(TrainerInfoTextBoxTileGraphics), (TrainerInfoTextBoxTileGraphicsEnd - TrainerInfoTextBoxTileGraphics) / $10
+	lb bc, BANK(TrainerInfoTextBoxTileGraphics), (TrainerInfoTextBoxTileGraphicsEnd - TrainerInfoTextBoxTileGraphics) / TILE_SIZE
 	jp CopyVideoData
diff --git a/engine/menus/display_text_id_init.asm b/engine/menus/display_text_id_init.asm
index f8bd6512..7ffdf7c3 100644
--- a/engine/menus/display_text_id_init.asm
+++ b/engine/menus/display_text_id_init.asm
@@ -43,8 +43,8 @@ DisplayTextIDInit::
 ; this is done because when you talk to an NPC, they turn to look your way
 ; the original direction they were facing must be restored after the dialogue is over
 	ld hl, wSprite01StateData1FacingDirection
-	ld c, $0f
-	ld de, $10
+	ld c, NUM_SPRITESTATEDATA_STRUCTS - 1
+	ld de, SPRITESTATEDATA1_LENGTH
 .spriteFacingDirectionCopyLoop
 	ld a, [hl] ; x#SPRITESTATEDATA1_FACINGDIRECTION
 	inc h
@@ -56,7 +56,8 @@ DisplayTextIDInit::
 ; loop to force all the sprites in the middle of animation to stand still
 ; (so that they don't like they're frozen mid-step during the dialogue)
 	ld hl, wSpritePlayerStateData1ImageIndex
-	ld de, $10
+	ld de, SPRITESTATEDATA1_LENGTH
+	ASSERT NUM_SPRITESTATEDATA_STRUCTS == SPRITESTATEDATA1_LENGTH
 	ld c, e
 .spriteStandStillLoop
 	ld a, [hl]
diff --git a/engine/menus/naming_screen.asm b/engine/menus/naming_screen.asm
index fda482e3..9c0cd0a8 100644
--- a/engine/menus/naming_screen.asm
+++ b/engine/menus/naming_screen.asm
@@ -327,7 +327,7 @@ LoadEDTile:
 	ld de, ED_Tile
 	ld hl, vFont tile $70
 	; BUG: BANK("Home") should be BANK(ED_Tile), although it coincidentally works as-is
-	lb bc, BANK("Home"), (ED_TileEnd - ED_Tile) / $8
+	lb bc, BANK("Home"), (ED_TileEnd - ED_Tile) / TILE_1BPP_SIZE
 	jp CopyVideoDataDouble
 
 ED_Tile:
diff --git a/engine/menus/save.asm b/engine/menus/save.asm
index 9dfdd949..3fab0d01 100644
--- a/engine/menus/save.asm
+++ b/engine/menus/save.asm
@@ -225,15 +225,15 @@ SaveMainData:
 	ld de, sSpriteData
 	ld bc, wSpriteDataEnd - wSpriteDataStart
 	call CopyData
-	ld hl, wBoxDataStart
 
 ; this part is redundant, SaveCurrentBoxData is always called next
+	ld hl, wBoxDataStart
 	ld de, sCurBoxData
 	ld bc, wBoxDataEnd - wBoxDataStart
 	call CopyData
+
 	ldh a, [hTileAnimations]
 	ld [sTileAnimations], a
-
 	ld hl, sGameData
 	ld bc, sGameDataEnd - sGameData
 	call CalcCheckSum
diff --git a/engine/menus/start_sub_menus.asm b/engine/menus/start_sub_menus.asm
index 8ba05b3f..c27e58a9 100644
--- a/engine/menus/start_sub_menus.asm
+++ b/engine/menus/start_sub_menus.asm
@@ -511,7 +511,7 @@ DrawTrainerInfo:
 	ld de, 13 tiles
 	add hl, de ; hl = colon tile pattern
 	ld de, vChars1 tile $56
-	ld bc, 1 tiles
+	ld bc, TILE_SIZE
 	ld a, BANK(TextBoxGraphics)
 	push bc
 	call FarCopyData2
@@ -677,13 +677,13 @@ SwitchPartyMon_ClearGfx:
 	dec c
 	jr nz, .clearMonBGLoop
 	pop af
-	ld hl, wShadowOAM
-	ld bc, $10
+	ld hl, wShadowOAMSprite00YCoord
+	ld bc, OBJ_SIZE * 4
 	call AddNTimes
-	ld de, $4
+	ld de, OBJ_SIZE
 	ld c, e
 .clearMonOAMLoop
-	ld [hl], $a0
+	ld [hl], SCREEN_HEIGHT_PX + OAM_Y_OFS
 	add hl, de
 	dec c
 	jr nz, .clearMonOAMLoop
diff --git a/engine/movie/credits.asm b/engine/movie/credits.asm
index 1a68a7b5..b1ca7c91 100644
--- a/engine/movie/credits.asm
+++ b/engine/movie/credits.asm
@@ -11,7 +11,7 @@ HallOfFamePC:
 	ld bc, ($20 tiles) / 2
 	call ZeroMemory
 	ld hl, vChars2 tile $7e
-	ld bc, 1 tiles
+	ld bc, TILE_SIZE
 	ld a, $ff ; solid black
 	call FillMemory
 	hlcoord 0, 0
@@ -246,7 +246,7 @@ Credits:
 	pop de
 	ld de, TheEndGfx
 	ld hl, vChars2 tile $60
-	lb bc, BANK(TheEndGfx), (TheEndGfxEnd - TheEndGfx) / $10
+	lb bc, BANK(TheEndGfx), (TheEndGfxEnd - TheEndGfx) / TILE_SIZE
 	call CopyVideoData
 	hlcoord 4, 8
 	ld de, TheEndTextString
diff --git a/engine/movie/intro.asm b/engine/movie/intro.asm
index 00316018..2fa442f9 100644
--- a/engine/movie/intro.asm
+++ b/engine/movie/intro.asm
@@ -439,12 +439,12 @@ IntroNidorinoAnimation7:
 GameFreakIntro:
 	INCBIN "gfx/splash/gamefreak_presents.2bpp"
 	INCBIN "gfx/splash/gamefreak_logo.2bpp"
-	ds 16, $00 ; blank tile
+	ds TILE_SIZE, $00 ; blank tile
 GameFreakIntroEnd:
 
 FightIntroBackMon:
 	INCBIN "gfx/intro/gengar.2bpp"
-	ds 16, $00 ; blank tile
+	ds TILE_SIZE, $00 ; blank tile
 FightIntroBackMonEnd:
 
 IF DEF(_RED)
diff --git a/engine/movie/oak_speech/oak_speech.asm b/engine/movie/oak_speech/oak_speech.asm
index 02826b98..a5f13def 100644
--- a/engine/movie/oak_speech/oak_speech.asm
+++ b/engine/movie/oak_speech/oak_speech.asm
@@ -117,6 +117,9 @@ OakSpeech:
 	ld a, SFX_SHRINK
 	call PlaySound
 	pop af
+; bug: switching ROM Bank should not happen outside of Home Bank
+; This code does nothing, as PlaySound does all necessary Bank switch
+; It looks like a leftover from an early development stage
 	ldh [hLoadedROMBank], a
 	ld [rROMB], a
 	ld c, 4
@@ -145,6 +148,7 @@ OakSpeech:
 	ld [wNewSoundID], a
 	call PlaySound
 	pop af
+; bug: switching ROM Bank should not happen outside of Home Bank
 	ldh [hLoadedROMBank], a
 	ld [rROMB], a
 	ld c, 20
@@ -160,21 +164,26 @@ OakSpeech:
 	call DelayFrames
 	call GBFadeOutToWhite
 	jp ClearScreen
+
 OakSpeechText1:
 	text_far _OakSpeechText1
 	text_end
+
 OakSpeechText2:
 	text_far _OakSpeechText2A
 	; BUG: The cry played does not match the sprite displayed.
 	sound_cry_nidorina
 	text_far _OakSpeechText2B
 	text_end
+
 IntroducePlayerText:
 	text_far _IntroducePlayerText
 	text_end
+
 IntroduceRivalText:
 	text_far _IntroduceRivalText
 	text_end
+
 OakSpeechText3:
 	text_far _OakSpeechText3
 	text_end
@@ -226,7 +235,7 @@ IntroDisplayPicCenteredOrUpperRight:
 	call UncompressSpriteFromDE
 	ld hl, sSpriteBuffer1
 	ld de, sSpriteBuffer0
-	ld bc, $310
+	ld bc, 2 * SPRITEBUFFERSIZE
 	call CopyData
 	ld de, vFrontPic
 	call InterlaceMergeSpriteBuffers
diff --git a/engine/movie/splash.asm b/engine/movie/splash.asm
index da3fec0d..7f06c68b 100644
--- a/engine/movie/splash.asm
+++ b/engine/movie/splash.asm
@@ -13,7 +13,7 @@ LoadShootingStarGraphics:
 	call CopyVideoData
 	ld de, FallingStar
 	ld hl, vChars1 tile $22
-	lb bc, BANK(FallingStar), (FallingStarEnd - FallingStar) / $10
+	lb bc, BANK(FallingStar), (FallingStarEnd - FallingStar) / TILE_SIZE
 	call CopyVideoData
 	ld hl, GameFreakLogoOAMData
 	ld de, wShadowOAMSprite24
@@ -60,11 +60,11 @@ AnimateShootingStar:
 	jr nz, .bigStarLoop
 
 ; Clear big star OAM.
-	ld hl, wShadowOAM
+	ld hl, wShadowOAMSprite00YCoord
 	ld c, 4
-	ld de, 4
+	ld de, OBJ_SIZE
 .clearOAMLoop
-	ld [hl], 160
+	ld [hl], SCREEN_HEIGHT_PX + OAM_Y_OFS
 	add hl, de
 	dec c
 	jr nz, .clearOAMLoop
diff --git a/engine/movie/title.asm b/engine/movie/title.asm
index 698dd5e0..c9ea4b47 100644
--- a/engine/movie/title.asm
+++ b/engine/movie/title.asm
@@ -104,7 +104,7 @@ DisplayTitleScreen:
 ; place tiles for title screen copyright
 	hlcoord 2, 17
 	ld de, .tileScreenCopyrightTiles
-	ld b, $10
+	ld b, .tileScreenCopyrightTilesEnd - .tileScreenCopyrightTiles
 .tileScreenCopyrightTilesLoop
 	ld a, [de]
 	ld [hli], a
@@ -116,6 +116,7 @@ DisplayTitleScreen:
 
 .tileScreenCopyrightTiles
 	db $41,$42,$43,$42,$44,$42,$45,$46,$47,$48,$49,$4A,$4B,$4C,$4D,$4E ; ©'95.'96.'98 GAME FREAK inc.
+.tileScreenCopyrightTilesEnd
 
 .next
 	call SaveScreenTilesToBuffer2
@@ -380,7 +381,7 @@ LoadCopyrightAndTextBoxTiles:
 LoadCopyrightTiles:
 	ld de, NintendoCopyrightLogoGraphics
 	ld hl, vChars2 tile $60
-	lb bc, BANK(NintendoCopyrightLogoGraphics), (GameFreakLogoGraphicsEnd - NintendoCopyrightLogoGraphics) / $10
+	lb bc, BANK(NintendoCopyrightLogoGraphics), (GameFreakLogoGraphicsEnd - NintendoCopyrightLogoGraphics) / TILE_SIZE
 	call CopyVideoData
 	hlcoord 2, 7
 	ld de, CopyrightTextString
diff --git a/engine/movie/trade.asm b/engine/movie/trade.asm
index bf77f21e..292f47cd 100644
--- a/engine/movie/trade.asm
+++ b/engine/movie/trade.asm
@@ -316,7 +316,7 @@ Trade_AnimateBallEnteringLinkCable:
 	ld [wLinkCableAnimBulgeToggle], a
 	add $7e
 	ld hl, wShadowOAMSprite00TileID
-	ld de, 4
+	ld de, OBJ_SIZE
 	ld c, e
 .cycleLinkCableBulgeTile
 	ld [hl], a
@@ -602,7 +602,7 @@ Trade_AnimCircledMon:
 	xor $3c ; make link cable flash
 	ldh [rBGP], a
 	ld hl, wShadowOAMSprite00TileID
-	ld de, $4
+	ld de, OBJ_SIZE
 	ld c, $14
 .loop
 	ld a, [hl]
diff --git a/engine/overworld/cut.asm b/engine/overworld/cut.asm
index 93902b51..368941d5 100644
--- a/engine/overworld/cut.asm
+++ b/engine/overworld/cut.asm
@@ -100,13 +100,13 @@ InitCutAnimOAM:
 	call LoadCutGrassAnimationTilePattern
 	call WriteCutOrBoulderDustAnimationOAMBlock
 	ld hl, wShadowOAMSprite36Attributes
-	ld de, 4
-	ld a, $30
+	ld de, OBJ_SIZE
+	ld a, OAM_XFLIP | OAM_PAL1
 	ld c, e
 .loop
 	ld [hl], a
 	add hl, de
-	xor $60
+	xor OAM_YFLIP | OAM_XFLIP
 	dec c
 	jr nz, .loop
 	ret
diff --git a/engine/overworld/dust_smoke.asm b/engine/overworld/dust_smoke.asm
index 96dd364a..85b89cdc 100644
--- a/engine/overworld/dust_smoke.asm
+++ b/engine/overworld/dust_smoke.asm
@@ -70,7 +70,7 @@ LoadSmokeTileFourTimes::
 	push hl
 	call LoadSmokeTile
 	pop hl
-	ld bc, 1 tiles
+	ld bc, TILE_SIZE
 	add hl, bc
 	pop bc
 	dec c
@@ -79,7 +79,7 @@ LoadSmokeTileFourTimes::
 
 LoadSmokeTile:
 	ld de, SSAnneSmokePuffTile
-	lb bc, BANK(SSAnneSmokePuffTile), (SSAnneSmokePuffTileEnd - SSAnneSmokePuffTile) / $10
+	lb bc, BANK(SSAnneSmokePuffTile), (SSAnneSmokePuffTileEnd - SSAnneSmokePuffTile) / TILE_SIZE
 	jp CopyVideoData
 
 SSAnneSmokePuffTile:
diff --git a/engine/overworld/ledges.asm b/engine/overworld/ledges.asm
index db8b9e97..69403042 100644
--- a/engine/overworld/ledges.asm
+++ b/engine/overworld/ledges.asm
@@ -59,7 +59,7 @@ INCLUDE "data/tilesets/ledge_tiles.asm"
 LoadHoppingShadowOAM:
 	ld hl, vChars1 tile $7f
 	ld de, LedgeHoppingShadow
-	lb bc, BANK(LedgeHoppingShadow), (LedgeHoppingShadowEnd - LedgeHoppingShadow) / $8
+	lb bc, BANK(LedgeHoppingShadow), (LedgeHoppingShadowEnd - LedgeHoppingShadow) / TILE_1BPP_SIZE
 	call CopyVideoDataDouble
 	ld a, $9
 	lb bc, $54, $48 ; b, c = y, x coordinates of shadow
diff --git a/engine/overworld/player_animations.asm b/engine/overworld/player_animations.asm
index c163b27e..4ed1f49f 100644
--- a/engine/overworld/player_animations.asm
+++ b/engine/overworld/player_animations.asm
@@ -209,13 +209,13 @@ LeaveMapThroughHoleAnim:
 	ld [wShadowOAMSprite02TileID], a
 	ld a, [wShadowOAMSprite01TileID]
 	ld [wShadowOAMSprite03TileID], a
-	ld a, $a0
+	ld a, SCREEN_HEIGHT_PX + OAM_Y_OFS
 	ld [wShadowOAMSprite00YCoord], a
 	ld [wShadowOAMSprite01YCoord], a
 	ld c, 2
 	call DelayFrames
 	; hide upper half of player's sprite
-	ld a, $a0
+	ld a, SCREEN_HEIGHT_PX + OAM_Y_OFS
 	ld [wShadowOAMSprite02YCoord], a
 	ld [wShadowOAMSprite03YCoord], a
 	call GBFadeOutToWhite
@@ -423,7 +423,7 @@ FishingAnim:
 	ld a, [wSpritePlayerStateData1ImageIndex] ; (image index is locked to standing images)
 	cp SPRITE_FACING_UP
 	jr nz, .skipHidingFishingRod
-	ld a, $a0
+	ld a, SCREEN_HEIGHT_PX + OAM_Y_OFS
 	ld [wShadowOAMSprite39YCoord], a
 
 .skipHidingFishingRod
diff --git a/home/clear_sprites.asm b/home/clear_sprites.asm
index 6d1066fa..c18b1ff3 100644
--- a/home/clear_sprites.asm
+++ b/home/clear_sprites.asm
@@ -9,10 +9,10 @@ ClearSprites::
 	ret
 
 HideSprites::
-	ld a, 160
-	ld hl, wShadowOAM
-	ld de, 4
-	ld b, 40
+	ld a, SCREEN_HEIGHT_PX + OAM_Y_OFS
+	ld hl, wShadowOAMSprite00YCoord
+	ld de, OBJ_SIZE
+	ld b, OAM_COUNT
 .loop
 	ld [hl], a
 	add hl, de
diff --git a/home/load_font.asm b/home/load_font.asm
index e886f76e..47ad60f1 100644
--- a/home/load_font.asm
+++ b/home/load_font.asm
@@ -11,7 +11,7 @@ LoadFontTilePatterns::
 .on
 	ld de, FontGraphics
 	ld hl, vFont
-	lb bc, BANK(FontGraphics), (FontGraphicsEnd - FontGraphics) / $8
+	lb bc, BANK(FontGraphics), (FontGraphicsEnd - FontGraphics) / TILE_1BPP_SIZE
 	jp CopyVideoDataDouble ; if LCD is on, transfer during V-blank
 
 LoadTextBoxTilePatterns::
@@ -27,7 +27,7 @@ LoadTextBoxTilePatterns::
 .on
 	ld de, TextBoxGraphics
 	ld hl, vChars2 tile $60
-	lb bc, BANK(TextBoxGraphics), (TextBoxGraphicsEnd - TextBoxGraphics) / $10
+	lb bc, BANK(TextBoxGraphics), (TextBoxGraphicsEnd - TextBoxGraphics) / TILE_SIZE
 	jp CopyVideoData ; if LCD is on, transfer during V-blank
 
 LoadHpBarAndStatusTilePatterns::
@@ -43,5 +43,5 @@ LoadHpBarAndStatusTilePatterns::
 .on
 	ld de, HpBarAndStatusGraphics
 	ld hl, vChars2 tile $62
-	lb bc, BANK(HpBarAndStatusGraphics), (HpBarAndStatusGraphicsEnd - HpBarAndStatusGraphics) / $10
+	lb bc, BANK(HpBarAndStatusGraphics), (HpBarAndStatusGraphicsEnd - HpBarAndStatusGraphics) / TILE_SIZE
 	jp CopyVideoData ; if LCD is on, transfer during V-blank
diff --git a/home/overworld.asm b/home/overworld.asm
index 5af527c0..f837815b 100644
--- a/home/overworld.asm
+++ b/home/overworld.asm
@@ -119,7 +119,7 @@ OverworldLoopLessDelay::
 	ld [wDestinationMap], a
 	call PrepareForSpecialWarp
 	ld a, [wCurMap]
-	call SwitchToMapRomBank ; switch to the ROM bank of the current map
+	call SwitchToMapRomBank
 	ld hl, wCurMapTileset
 	set BIT_NO_PREVIOUS_MAP, [hl]
 .changeMap
@@ -506,7 +506,7 @@ WarpFound2::
 ; for maps that can have the 0xFF destination map, which means to return to the outside map
 ; not all these maps are necessarily indoors, though
 .indoorMaps
-	ldh a, [hWarpDestinationMap] ; destination map
+	ldh a, [hWarpDestinationMap]
 	cp LAST_MAP
 	jr z, .goBackOutside
 ; if not going back to the previous map
@@ -567,7 +567,7 @@ CheckMapConnections::
 	srl c
 	jr z, .savePointer1
 .pointerAdjustmentLoop1
-	ld a, [wWestConnectedMapWidth] ; width of connected map
+	ld a, [wWestConnectedMapWidth]
 	add MAP_BORDER * 2
 	ld e, a
 	ld d, 0
@@ -584,7 +584,7 @@ CheckMapConnections::
 
 .checkEastMap
 	ld b, a
-	ld a, [wCurrentMapWidth2] ; map width
+	ld a, [wCurrentMapWidth2]
 	cp b
 	jr nz, .checkNorthMap
 	ld a, [wEastConnectedMap]
@@ -1171,7 +1171,7 @@ IsSpriteInFrontOfPlayer2::
 	ld a, PLAYER_DIR_LEFT
 .doneCheckingDirection
 	ld [wPlayerDirection], a
-	ld a, [wNumSprites] ; number of sprites
+	ld a, [wNumSprites]
 	and a
 	ret z
 ; if there are sprites
@@ -1198,7 +1198,7 @@ IsSpriteInFrontOfPlayer2::
 .nextSprite
 	pop hl
 	ld a, l
-	add $10
+	add SPRITESTATEDATA1_LENGTH
 	ld l, a
 	inc e
 	dec d
@@ -1258,8 +1258,8 @@ CollisionCheckOnLand::
 ; function that checks if the tile in front of the player is passable
 ; clears carry if it is, sets carry if not
 CheckTilePassable::
-	predef GetTileAndCoordsInFrontOfPlayer ; get tile in front of player
-	ld a, [wTileInFrontOfPlayer] ; tile in front of player
+	predef GetTileAndCoordsInFrontOfPlayer
+	ld a, [wTileInFrontOfPlayer]
 	ld c, a
 	ld hl, wTilesetCollisionPtr ; pointer to list of passable tiles
 	ld a, [hli]
@@ -1282,7 +1282,7 @@ CheckTilePassable::
 ; sets carry if there is a collision and unsets carry if not
 CheckForJumpingAndTilePairCollisions::
 	push hl
-	predef GetTileAndCoordsInFrontOfPlayer ; get the tile in front of the player
+	predef GetTileAndCoordsInFrontOfPlayer
 	push de
 	push bc
 	farcall HandleLedges ; check if the player is trying to jump a ledge
@@ -1315,7 +1315,7 @@ CheckForTilePairCollisions::
 	inc hl
 	jr .tilePairCollisionLoop
 .tilesetMatches
-	ld a, [wTilePlayerStandingOn] ; tile the player is on
+	ld a, [wTilePlayerStandingOn]
 	ld b, a
 	ld a, [hl]
 	cp b
@@ -1350,9 +1350,9 @@ INCLUDE "data/tilesets/pair_collision_tile_ids.asm"
 LoadCurrentMapView::
 	ldh a, [hLoadedROMBank]
 	push af
-	ld a, [wTilesetBank] ; tile data ROM bank
+	ld a, [wTilesetBank]
 	ldh [hLoadedROMBank], a
-	ld [rROMB], a ; switch to ROM bank that contains tile data
+	ld [rROMB], a
 	ld a, [wCurrentTileBlockMapViewPointer] ; address of upper left corner of current map view
 	ld e, a
 	ld a, [wCurrentTileBlockMapViewPointer + 1]
@@ -1434,7 +1434,7 @@ LoadCurrentMapView::
 	jr nz, .rowLoop2
 	pop af
 	ldh [hLoadedROMBank], a
-	ld [rROMB], a ; restore previous ROM bank
+	ld [rROMB], a
 	ret
 
 AdvancePlayerSprite::
@@ -1442,7 +1442,7 @@ AdvancePlayerSprite::
 	ld b, a
 	ld a, [wSpritePlayerStateData1XStepVector]
 	ld c, a
-	ld hl, wWalkCounter ; walking animation counter
+	ld hl, wWalkCounter
 	dec [hl]
 	jr nz, .afterUpdateMapCoords
 ; if it's the end of the animation, update the player's map coordinates
@@ -1453,7 +1453,7 @@ AdvancePlayerSprite::
 	add c
 	ld [wXCoord], a
 .afterUpdateMapCoords
-	ld a, [wWalkCounter] ; walking animation counter
+	ld a, [wWalkCounter]
 	cp $07
 	jp nz, .scrollBackgroundAndSprites
 ; if this is the first iteration of the animation
@@ -1612,7 +1612,7 @@ AdvancePlayerSprite::
 ; shift all the sprites in the direction opposite of the player's motion
 ; so that the player appears to move relative to them
 	ld hl, wSprite01StateData1YPixels
-	ld a, [wNumSprites] ; number of sprites
+	ld a, [wNumSprites]
 	and a ; are there any sprites?
 	jr z, .done
 	ld e, a
@@ -2151,8 +2151,8 @@ LoadMapHeader::
 	jr nz, .zeroSpriteDataLoop
 ; disable SPRITESTATEDATA1_IMAGEINDEX (set to $ff) for sprites 01-15
 	ld hl, wSprite01StateData1ImageIndex
-	ld de, $10
-	ld c, $0f
+	ld de, SPRITESTATEDATA1_LENGTH
+	ld c, NUM_SPRITESTATEDATA_STRUCTS - 1
 .disableSpriteEntriesLoop
 	ld [hl], $ff
 	add hl, de
@@ -2296,7 +2296,7 @@ LoadMapData::
 	ldh a, [hLoadedROMBank]
 	push af
 	call DisableLCD
-	ld a, $98
+	ld a, HIGH(vBGMap0)
 	ld [wMapViewVRAMPointer + 1], a
 	xor a
 	ld [wMapViewVRAMPointer], a
diff --git a/home/pics.asm b/home/pics.asm
index ea34e3d5..475e834d 100644
--- a/home/pics.asm
+++ b/home/pics.asm
@@ -127,8 +127,8 @@ AlignSpriteDataCentered::
 	dec c
 	jr nz, .columnInnerLoop
 	pop hl
-	ld bc, 7*8    ; 7 tiles
-	add hl, bc    ; advance one full column
+	ld bc, 7 * TILE_1BPP_SIZE
+	add hl, bc ; advance one full column
 	pop af
 	dec a
 	jr nz, .columnLoop
@@ -156,7 +156,7 @@ InterlaceMergeSpriteBuffers::
 	ld hl, sSpriteBuffer2 + (SPRITEBUFFERSIZE - 1) ; destination: end of buffer 2
 	ld de, sSpriteBuffer1 + (SPRITEBUFFERSIZE - 1) ; source 2: end of buffer 1
 	ld bc, sSpriteBuffer0 + (SPRITEBUFFERSIZE - 1) ; source 1: end of buffer 0
-	ld a, SPRITEBUFFERSIZE/2 ; $c4
+	ld a, SPRITEBUFFERSIZE / 2
 	ldh [hSpriteInterlaceCounter], a
 .interlaceLoop
 	ld a, [de]
@@ -178,7 +178,7 @@ InterlaceMergeSpriteBuffers::
 	ld a, [wSpriteFlipped]
 	and a
 	jr z, .notFlipped
-	ld bc, 2*SPRITEBUFFERSIZE
+	ld bc, 2 * SPRITEBUFFERSIZE
 	ld hl, sSpriteBuffer1
 .swapLoop
 	swap [hl]    ; if flipped swap nybbles in all bytes
@@ -190,7 +190,7 @@ InterlaceMergeSpriteBuffers::
 .notFlipped
 	pop hl
 	ld de, sSpriteBuffer1
-	ld c, (2*SPRITEBUFFERSIZE)/16 ; $31, number of 16 byte chunks to be copied
+	ld c, (2 * SPRITEBUFFERSIZE) / TILE_SIZE ; $31, number of 16 byte chunks to be copied
 	ldh a, [hLoadedROMBank]
 	ld b, a
 	jp CopyVideoData
diff --git a/home/reset_player_sprite.asm b/home/reset_player_sprite.asm
index 72df31a1..6ce4a6fa 100644
--- a/home/reset_player_sprite.asm
+++ b/home/reset_player_sprite.asm
@@ -15,6 +15,7 @@ ResetPlayerSpriteData::
 
 ; overwrites sprite data with zeroes
 ResetPlayerSpriteData_ClearSpriteData::
-	ld bc, $10
+	ld bc, SPRITESTATEDATA1_LENGTH
+	ASSERT SPRITESTATEDATA2_LENGTH == SPRITESTATEDATA1_LENGTH
 	xor a
 	jp FillMemory
diff --git a/home/text_script.asm b/home/text_script.asm
index 389f2499..36f6338b 100644
--- a/home/text_script.asm
+++ b/home/text_script.asm
@@ -113,8 +113,8 @@ CloseTextDisplay::
 	ldh [hAutoBGTransferEnabled], a ; disable continuous WRAM to VRAM transfer each V-blank
 ; loop to make sprites face the directions they originally faced before the dialogue
 	ld hl, wSprite01StateData2OrigFacingDirection
-	ld c, $0f
-	ld de, $10
+	ld c, NUM_SPRITESTATEDATA_STRUCTS - 1
+	ld de, SPRITESTATEDATA1_LENGTH
 .restoreSpriteFacingDirectionLoop
 	ld a, [hl] ; x#SPRITESTATEDATA2_ORIGFACINGDIRECTION
 	dec h
diff --git a/home/vcopy.asm b/home/vcopy.asm
index 8ae9484a..cf4c3e6c 100644
--- a/home/vcopy.asm
+++ b/home/vcopy.asm
@@ -20,9 +20,14 @@ GetRowColAddressBgMap::
 ; INPUT: h - high byte of background tile map address in VRAM
 ClearBgMap::
 	ld a, ' '
-	jr .next
+	jr FillBgMapCommon
+
+; fills a VRAM background map with tile index in register l
+; INPUT: h - high byte of background tile map address in VRAM
+FillBgMap:: ; unreferenced
 	ld a, l
-.next
+
+FillBgMapCommon:
 	ld de, TILEMAP_AREA
 	ld l, e
 .loop
@@ -69,8 +74,8 @@ RedrawRowOrColumn::
 .noCarry
 ; the following 4 lines wrap us from bottom to top if necessary
 	ld a, d
-	and $3
-	or $98
+	and HIGH(TILEMAP_AREA - 1)
+	or HIGH(vBGMap0)
 	ld d, a
 	dec c
 	jr nz, .loop1
@@ -86,7 +91,7 @@ RedrawRowOrColumn::
 	push de
 	call .DrawHalf ; draw upper half
 	pop de
-	ld a, TILEMAP_WIDTH ; width of VRAM background map
+	ld a, TILEMAP_WIDTH
 	add e
 	ld e, a
 	; fall through and draw lower half
@@ -102,10 +107,10 @@ RedrawRowOrColumn::
 	ld a, e
 	inc a
 ; the following 6 lines wrap us from the right edge to the left edge if necessary
-	and $1f
+	and %11111
 	ld b, a
 	ld a, e
-	and $e0
+	and %11100000
 	or b
 	ld e, a
 	dec c
@@ -134,7 +139,7 @@ AutoBgMapTransfer::
 	dec a
 	jr z, .transferMiddleThird
 .transferBottomThird
-	hlcoord 0, 12
+	hlcoord 0, 2 * SCREEN_HEIGHT / 3
 	ld sp, hl
 	ldh a, [hAutoBGTransferDest + 1]
 	ld h, a
@@ -154,7 +159,7 @@ AutoBgMapTransfer::
 	ld a, TRANSFERMIDDLE
 	jr .doTransfer
 .transferMiddleThird
-	hlcoord 0, 6
+	hlcoord 0, SCREEN_HEIGHT / 3
 	ld sp, hl
 	ldh a, [hAutoBGTransferDest + 1]
 	ld h, a
@@ -165,7 +170,7 @@ AutoBgMapTransfer::
 	ld a, TRANSFERBOTTOM
 .doTransfer
 	ldh [hAutoBGTransferPortion], a ; store next portion
-	ld b, 6
+	ld b, SCREEN_HEIGHT / 3
 
 TransferBgRows::
 ; unrolled loop and using pop for speed
@@ -390,7 +395,7 @@ UpdateMovingBgTiles::
 ; water
 
 	ld hl, vTileset tile $14
-	ld c, $10
+	ld c, TILE_SIZE
 
 	ld a, [wMovingBGTilesCounter2]
 	inc a
@@ -435,7 +440,7 @@ UpdateMovingBgTiles::
 	ld hl, FlowerTile3
 .copy
 	ld de, vTileset tile $03
-	ld c, $10
+	ld c, TILE_SIZE
 .loop
 	ld a, [hli]
 	ld [de], a
diff --git a/ram/wram.asm b/ram/wram.asm
index 0121b065..ff7d10ae 100644
--- a/ram/wram.asm
+++ b/ram/wram.asm
@@ -363,7 +363,7 @@ wFilteredBagItems:: ds 4
 NEXTU
 ; Saved copy of OAM for the first frame of the animation to make it easy to
 ; flip back from the second frame.
-wMonPartySpritesSavedOAM:: ds $60
+wMonPartySpritesSavedOAM:: ds OBJ_SIZE * 4 * PARTY_LENGTH
 
 NEXTU
 wTrainerCardBlkPacket:: ds $40
@@ -401,7 +401,7 @@ wAnimPalette:: db
 NEXTU
 	ds 60
 ; temporary buffer when swapping party mon data
-wSwitchPartyMonTempBuffer:: ds 44 ; party_struct size
+wSwitchPartyMonTempBuffer:: ds PARTYMON_STRUCT_LENGTH
 
 NEXTU
 	ds 120
@@ -1806,7 +1806,7 @@ wWestConnectionHeader::  map_connection_struct wWest
 wEastConnectionHeader::  map_connection_struct wEast
 
 ; sprite set for the current map (11 sprite picture ID's)
-wSpriteSet:: ds 11
+wSpriteSet:: ds SPRITE_SET_LENGTH
 ; sprite set ID for the current map
 wSpriteSetID:: db
 
diff --git a/scripts/VermilionDock.asm b/scripts/VermilionDock.asm
index 237b4175..beb53112 100644
--- a/scripts/VermilionDock.asm
+++ b/scripts/VermilionDock.asm
@@ -128,7 +128,7 @@ VermilionDock_AnimSmokePuffDriftRight:
 	ld a, [wSSAnneSmokeDriftAmount]
 	swap a
 	ld c, a
-	ld de, 4
+	ld de, OBJ_SIZE
 .drift_loop
 	inc [hl]
 	inc [hl]