Identify more bit flags

engine/events/hidden_objects/indigo_plateau_statues.asm

@@ -3,7 +3,7 @@ IndigoPlateauStatues::
 	ld hl, IndigoPlateauStatuesText1
 	call PrintText
 	ld a, [wXCoord]
-	bit 0, a
+	bit 0, a ; even or odd?
 	ld hl, IndigoPlateauStatuesText2
 	jr nz, .ok
 	ld hl, IndigoPlateauStatuesText3

engine/gfx/mon_icons.asm

@@ -269,7 +269,7 @@ GetPartyMonSpriteID:
 	ld d, 0
 	add hl, de
 	ld a, [hl]
-	bit 0, c
+	bit 0, c; even or odd?
 	jr nz, .skipSwap
 	swap a ; use lower nybble if pokedex num is even
 .skipSwap

engine/gfx/screen_effects.asm

@@ -61,7 +61,7 @@ PredefShakeScreenHorizontally:
 	ldh a, [hMutateWX]
 	xor b
 	ldh [hMutateWX], a
-	bit 7, a
+	bit 7, a ; negative?
 	jr z, .skipZeroing
 	xor a ; zero a if it's negative
 .skipZeroing

engine/movie/oak_speech/oak_speech.asm

@@ -4,9 +4,9 @@ PrepareOakSpeech:
 	ld a, [wOptions]
 	push af
 	; Retrieve BIT_DEBUG_MODE set in DebugMenu for StartNewGameDebug.
-	; BUG: StartNewGame carries over bit 5 from previous save files,
+	; BUG: StartNewGame carries over BIT_ALWAYS_ON_BIKE from previous save files,
 	; which causes CheckForceBikeOrSurf to not return.
-	; To fix this in debug builds, reset bit 5 here or in StartNewGame.
+	; To fix this in debug builds, reset BIT_ALWAYS_ON_BIKE here or in StartNewGame.
 	; In non-debug builds, the instructions can be removed.
 	ld a, [wStatusFlags6]
 	push af

engine/overworld/map_sprites.asm

@@ -187,7 +187,7 @@ LoadMapSpriteTilePatterns:
 	jr nz, .loadWhileLCDOn
 	pop af
 	pop hl
-	set 3, h ; add $80 tiles to hl
+	set 3, h ; add $800 ($80 tiles) to hl (1 << 3 == $8)
 	push hl
 	ld h, d
 	ld l, e
@@ -200,7 +200,7 @@ LoadMapSpriteTilePatterns:
 .loadWhileLCDOn
 	pop af
 	pop hl
-	set 3, h ; add $80 tiles to hl
+	set 3, h ; add $800 ($80 tiles) to hl (1 << 3 == $8)
 	ld b, a
 	swap c
 	call CopyVideoData ; load tile pattern data for sprite when walking

engine/overworld/movement.asm

@@ -641,7 +641,7 @@ CanWalkOntoTile:
 	add SPRITESTATEDATA2_YDISPLACEMENT
 	ld l, a
 	ld a, [hli]        ; x#SPRITESTATEDATA2_YDISPLACEMENT (initialized at $8, keep track of where a sprite did go)
-	bit 7, d           ; check if going upwards (d=$ff)
+	bit 7, d           ; check if going upwards (d == -1)
 	jr nz, .upwards
 	add d
 	; bug: these tests against $5 probably were supposed to prevent
@@ -658,7 +658,7 @@ CanWalkOntoTile:
 .checkHorizontal
 	ld d, a
 	ld a, [hl]         ; x#SPRITESTATEDATA2_XDISPLACEMENT (initialized at $8, keep track of where a sprite did go)
-	bit 7, e           ; check if going left (e=$ff)
+	bit 7, e           ; check if going left (e == -1)
 	jr nz, .left
 	add e
 	cp $5              ; compare, but no conditional jump like in the vertical check above (bug?)

engine/overworld/player_state.asm

@@ -294,6 +294,13 @@ _GetTileAndCoordsInFrontOfPlayer:
 	ld [wTileInFrontOfPlayer], a
 	ret
 
+; hPlayerFacing
+	const_def
+	const BIT_FACING_DOWN  ; 0
+	const BIT_FACING_UP    ; 1
+	const BIT_FACING_LEFT  ; 2
+	const BIT_FACING_RIGHT ; 3
+
 GetTileTwoStepsInFrontOfPlayer:
 	xor a
 	ldh [hPlayerFacing], a
@@ -306,7 +313,7 @@ GetTileTwoStepsInFrontOfPlayer:
 	jr nz, .notFacingDown
 ; facing down
 	ld hl, hPlayerFacing
-	set 0, [hl]
+	set BIT_FACING_DOWN, [hl]
 	lda_coord 8, 13
 	inc d
 	jr .storeTile
@@ -315,7 +322,7 @@ GetTileTwoStepsInFrontOfPlayer:
 	jr nz, .notFacingUp
 ; facing up
 	ld hl, hPlayerFacing
-	set 1, [hl]
+	set BIT_FACING_UP, [hl]
 	lda_coord 8, 5
 	dec d
 	jr .storeTile
@@ -324,7 +331,7 @@ GetTileTwoStepsInFrontOfPlayer:
 	jr nz, .notFacingLeft
 ; facing left
 	ld hl, hPlayerFacing
-	set 2, [hl]
+	set BIT_FACING_LEFT, [hl]
 	lda_coord 4, 9
 	dec e
 	jr .storeTile
@@ -333,7 +340,7 @@ GetTileTwoStepsInFrontOfPlayer:
 	jr nz, .storeTile
 ; facing right
 	ld hl, hPlayerFacing
-	set 3, [hl]
+	set BIT_FACING_RIGHT, [hl]
 	lda_coord 12, 9
 	inc e
 .storeTile
@@ -385,7 +392,7 @@ CheckForBoulderCollisionWithSprites:
 	ld de, $f
 	ld hl, wSprite01StateData2MapY
 	ldh a, [hPlayerFacing]
-	and $3 ; facing up or down?
+	and (1 << BIT_FACING_UP) | (1 << BIT_FACING_DOWN)
 	jr z, .pushingHorizontallyLoop
 .pushingVerticallyLoop
 	inc hl
@@ -396,6 +403,7 @@ CheckForBoulderCollisionWithSprites:
 	ld a, [hli]
 	ld b, a
 	ldh a, [hPlayerFacing]
+	assert BIT_FACING_DOWN == 0
 	rrca
 	jr c, .pushingDown
 ; pushing up
@@ -421,7 +429,7 @@ CheckForBoulderCollisionWithSprites:
 	jr nz, .nextSprite2
 	ld b, [hl]
 	ldh a, [hPlayerFacing]
-	bit 2, a
+	bit BIT_FACING_LEFT, a
 	jr nz, .pushingLeft
 ; pushing right
 	ldh a, [hPlayerXCoord]

engine/overworld/spinners.asm

@@ -15,7 +15,7 @@ LoadSpinnerArrowTiles::
 	ld hl, GymSpinnerArrows
 .gotSpinnerArrows
 	ld a, [wSimulatedJoypadStatesIndex]
-	bit 0, a
+	bit 0, a ; even or odd?
 	jr nz, .alternateGraphics
 	ld de, 6 * 4
 	add hl, de

home/overworld.asm

@@ -2002,7 +2002,7 @@ LoadPlayerSpriteGraphicsCommon::
 	jr nc, .noCarry
 	inc d
 .noCarry
-	set 3, h
+	set 3, h ; add $800 ($80 tiles) to hl (1 << 3 == $8)
 	lb bc, BANK(RedSprite), $0c
 	jp CopyVideoData
 

home/pokemon.asm

@@ -252,7 +252,7 @@ HandlePartyMenuInput::
 	jp nz, .swappingPokemon
 	pop af
 	ldh [hTileAnimations], a
-	bit 1, b
+	bit BIT_B_BUTTON, b
 	jr nz, .noPokemonChosen
 	ld a, [wPartyCount]
 	and a

home/serial.asm

@@ -30,7 +30,7 @@ Serial::
 	ldh [rDIV], a
 .waitLoop
 	ldh a, [rDIV]
-	bit 7, a
+	bit 7, a ; wait until rDIV has incremented from $3 to $80 or more
 	jr nz, .waitLoop
 	ld a, START_TRANSFER_EXTERNAL_CLOCK
 	ldh [rSC], a

home/uncompress.asm

@@ -1,3 +1,8 @@
+; wSpriteLoadFlags bits, streamed from compressed sprite data
+	const_def
+	const BIT_USE_SPRITE_BUFFER_2 ; 0
+	const BIT_LAST_SPRITE_CHUNK   ; 1
+
 ; bankswitches and runs _UncompressSpriteData
 ; bank is given in a, sprite input stream is pointed to in wSpriteInputPtr
 UncompressSpriteData::
@@ -47,7 +52,7 @@ _UncompressSpriteData::
 	add a
 	ld [wSpriteWidth], a
 	call ReadNextInputBit
-	ld [wSpriteLoadFlags], a ; initialite bit1 to 0 and bit0 to the first input bit
+	ld [wSpriteLoadFlags], a ; initialize bit1 to 0 and bit0 to the first input bit
                              ; this will load two chunks of data to sSpriteBuffer1 and sSpriteBuffer2
                              ; bit 0 decides in which one the first chunk is placed
 	; fall through
@@ -58,13 +63,13 @@ _UncompressSpriteData::
 UncompressSpriteDataLoop::
 	ld hl, sSpriteBuffer1
 	ld a, [wSpriteLoadFlags]
-	bit 0, a
+	bit BIT_USE_SPRITE_BUFFER_2, a
 	jr z, .useSpriteBuffer1    ; check which buffer to use
 	ld hl, sSpriteBuffer2
 .useSpriteBuffer1
 	call StoreSpriteOutputPointer
 	ld a, [wSpriteLoadFlags]
-	bit 1, a
+	bit BIT_LAST_SPRITE_CHUNK, a
 	jr z, .startDecompression  ; check if last iteration
 	call ReadNextInputBit      ; if last chunk, read 1-2 bit unpacking mode
 	and a
@@ -196,10 +201,10 @@ MoveToNextBufferPosition::
 	xor a
 	ld [wSpriteCurPosX], a
 	ld a, [wSpriteLoadFlags]
-	bit 1, a
+	bit BIT_LAST_SPRITE_CHUNK, a
 	jr nz, .done            ; test if there is one more sprite to go
-	xor $1
-	set 1, a
+	xor 1 << BIT_USE_SPRITE_BUFFER_2
+	set BIT_LAST_SPRITE_CHUNK, a
 	ld [wSpriteLoadFlags], a
 	jp UncompressSpriteDataLoop
 .done
@@ -540,7 +545,7 @@ ReverseNybble::
 ; resets sprite buffer pointers to buffer 1 and 2, depending on wSpriteLoadFlags
 ResetSpriteBufferPointers::
 	ld a, [wSpriteLoadFlags]
-	bit 0, a
+	bit BIT_USE_SPRITE_BUFFER_2, a
 	jr nz, .buffer2Selected
 	ld de, sSpriteBuffer1
 	ld hl, sSpriteBuffer2

scripts/VictoryRoad2F.asm

@@ -27,7 +27,7 @@ VictoryRoad2FCheckBoulderEventScript:
 	call VictoryRoad2FReplaceTileBlockScript
 	pop af
 .not_on_switch
-	bit 7, a
+	CheckEventReuseA EVENT_VICTORY_ROAD_2_BOULDER_ON_SWITCH2
 	ret z
 	ld a, $1d
 	lb bc, 7, 11