ref: 54c1893d579cdf6853c6a64953bae281a6075fe3
dir: /engine/overworld/movement.asm/
UpdatePlayerSprite: ; 4e31 (1:4e31) ld a, [wSpriteStateData2] and a jr z, .checkIfTextBoxInFrontOfSprite cp $ff jr z, .disableSprite dec a ld [wSpriteStateData2], a jr .disableSprite ; check if a text box is in front of the sprite by checking if the lower left ; background tile the sprite is standing on is greater than $5F, which is ; the maximum number for map tiles .checkIfTextBoxInFrontOfSprite aCoord 8, 9 ld [hTilePlayerStandingOn], a cp $60 jr c, .lowerLeftTileIsMapTile .disableSprite ld a, $ff ld [wSpriteStateData1 + 2], a ret .lowerLeftTileIsMapTile call DetectCollisionBetweenSprites ld h, wSpriteStateData1 / $100 ld a, [wWalkCounter] and a jr nz, .moving ld a, [wd528] ; check if down bit 2, a jr z, .checkIfUp xor a ; ld a, SPRITE_FACING_DOWN jr .next .checkIfUp bit 3, a jr z, .checkIfLeft ld a, SPRITE_FACING_UP jr .next .checkIfLeft bit 1, a jr z, .checkIfRight ld a, SPRITE_FACING_LEFT jr .next .checkIfRight bit 0, a jr z, .notMoving ld a, SPRITE_FACING_RIGHT jr .next .notMoving ; zero the animation counters xor a ld [wSpriteStateData1 + 7], a ld [wSpriteStateData1 + 8], a jr .calcImageIndex .next ld [wSpriteStateData1 + 9], a ; facing direction ld a, [wFontLoaded] bit 0, a jr nz, .notMoving .moving ld a, [wd736] bit 7, a ; is the player sprite spinning due to a spin tile? jr nz, .skipSpriteAnim ld a, [H_CURRENTSPRITEOFFSET] add $7 ld l, a ld a, [hl] inc a ld [hl], a cp 4 jr nz, .calcImageIndex xor a ld [hl], a inc hl ld a, [hl] inc a and $3 ld [hl], a .calcImageIndex ld a, [wSpriteStateData1 + 8] ld b, a ld a, [wSpriteStateData1 + 9] add b ld [wSpriteStateData1 + 2], a .skipSpriteAnim ; If the player is standing on a grass tile, make the player's sprite have ; lower priority than the background so that it's partially obscured by the ; grass. Only the lower half of the sprite is permitted to have the priority ; bit set by later logic. ld a, [hTilePlayerStandingOn] ld c, a ld a, [W_GRASSTILE] cp c ld a, $0 jr nz, .next2 ld a, $80 .next2 ld [wSpriteStateData2 + $07], a ret UnusedReadSpriteDataFunction: ; 4ec7 (1:4ec7) push bc push af ld a, [H_CURRENTSPRITEOFFSET] ld c, a pop af add c ld l, a pop bc ret UpdateNPCSprite: ; 4ed1 (1:4ed1) ld a, [H_CURRENTSPRITEOFFSET] swap a dec a add a ld hl, W_MAPSPRITEDATA add l ld l, a ld a, [hl] ; read movement byte 2 ld [wCurSpriteMovement2], a ld h, $c1 ld a, [H_CURRENTSPRITEOFFSET] ld l, a inc l ld a, [hl] ; c1x1 and a jp z, InitializeSpriteStatus call CheckSpriteAvailability ret c ; if sprite is invisible, on tile >=$60, in grass or player is currently walking ld h, $c1 ld a, [H_CURRENTSPRITEOFFSET] ld l, a inc l ld a, [hl] ; c1x1 bit 7, a jp nz, InitializeSpriteFacingDirection ; c1x1 >= $80 ld b, a ld a, [wFontLoaded] bit 0, a jp nz, notYetMoving ld a, b cp $2 jp z, UpdateSpriteMovementDelay ; c1x1 == 2 cp $3 jp z, UpdateSpriteInWalkingAnimation ; c1x1 == 3 ld a, [wWalkCounter] and a ret nz ; don't do anything yet if player is currently moving (redundant, already tested in CheckSpriteAvailability) call InitializeSpriteScreenPosition ld h, $c2 ld a, [H_CURRENTSPRITEOFFSET] add $6 ld l, a ld a, [hl] ; c2x6: movement byte 1 inc a jr z, .randomMovement ; value $FF inc a jr z, .randomMovement ; value $FE ; scripted movement dec a ld [hl], a ; increment movement byte 1 (movement data index) dec a push hl ld hl, wNPCNumScriptedSteps dec [hl] ; decrement wNPCNumScriptedSteps pop hl ld de, wNPCMovementDirections call LoadDEPlusA ; a = [wNPCMovementDirections + movement byte 1] cp $e0 jp z, ChangeFacingDirection cp $ff jr nz, .next ; reached end of wNPCMovementDirections list ld [hl], a ; store $ff in movement byte 1, disabling scripted movement ld hl, wd730 res 0, [hl] xor a ld [wSimulatedJoypadStatesIndex], a ld [wWastedByteCD3A], a ret .next cp $fe jr nz, .determineDirection ; current NPC movement data is $fe. this seems buggy ld [hl], $1 ; set movement byte 1 to $1 ld de, wNPCMovementDirections call LoadDEPlusA ; a = [wNPCMovementDirections + $fe] (?) jr .determineDirection .randomMovement call GetTileSpriteStandsOn call Random .determineDirection ld b, a ld a, [wCurSpriteMovement2] cp $d0 jr z, .moveDown ; movement byte 2 = $d0 forces down cp $d1 jr z, .moveUp ; movement byte 2 = $d1 forces up cp $d2 jr z, .moveLeft ; movement byte 2 = $d2 forces left cp $d3 jr z, .moveRight ; movement byte 2 = $d3 forces right ld a, b cp $40 ; a < $40: down (or left) jr nc, .notDown ld a, [wCurSpriteMovement2] cp $2 jr z, .moveLeft ; movement byte 2 = $2 only allows left or right .moveDown ld de, 2*SCREEN_WIDTH add hl, de ; move tile pointer two rows down ld de, $100 ld bc, $400 jr TryWalking .notDown cp $80 ; $40 <= a < $80: up (or right) jr nc, .notUp ld a, [wCurSpriteMovement2] cp $2 jr z, .moveRight ; movement byte 2 = $2 only allows left or right .moveUp ld de, -2*SCREEN_WIDTH add hl, de ; move tile pointer two rows up ld de, $ff00 ld bc, $804 jr TryWalking .notUp cp $c0 ; $80 <= a < $c0: left (or up) jr nc, .notLeft ld a, [wCurSpriteMovement2] cp $1 jr z, .moveUp ; movement byte 2 = $1 only allows up or down .moveLeft dec hl dec hl ; move tile pointer two columns left ld de, $ff ld bc, $208 jr TryWalking .notLeft ; $c0 <= a: right (or down) ld a, [wCurSpriteMovement2] cp $1 jr z, .moveDown ; movement byte 2 = $1 only allows up or down .moveRight inc hl inc hl ; move tile pointer two columns right ld de, $1 ld bc, $10c jr TryWalking ; changes facing direction by zeroing the movement delta and calling TryWalking ChangeFacingDirection: ; 4fc8 (1:4fc8) ld de, $0 ; fall through ; b: direction (1,2,4 or 8) ; c: new facing direction (0,4,8 or $c) ; d: Y movement delta (-1, 0 or 1) ; e: X movement delta (-1, 0 or 1) ; hl: pointer to tile the sprite would walk onto ; set carry on failure, clears carry on success TryWalking: ; 4fcb (1:4fcb) push hl ld h, $c1 ld a, [H_CURRENTSPRITEOFFSET] add $9 ld l, a ld [hl], c ; c1x9 (update facing direction) ld a, [H_CURRENTSPRITEOFFSET] add $3 ld l, a ld [hl], d ; c1x3 (update Y movement delta) inc l inc l ld [hl], e ; c1x5 (update X movement delta) pop hl push de ld c, [hl] ; read tile to walk onto call CanWalkOntoTile pop de ret c ; cannot walk there (reinitialization of delay values already done) ld h, $c2 ld a, [H_CURRENTSPRITEOFFSET] add $4 ld l, a ld a, [hl] ; c2x4: Y position add d ld [hli], a ; update Y position ld a, [hl] ; c2x5: X position add e ld [hl], a ; update X position ld a, [H_CURRENTSPRITEOFFSET] ld l, a ld [hl], $10 ; c2x0=16: walk animation counter dec h inc l ld [hl], $3 ; c1x1: set movement status to walking jp UpdateSpriteImage ; update the walking animation parameters for a sprite that is currently walking UpdateSpriteInWalkingAnimation: ; 4ffe (1:4ffe) ld a, [H_CURRENTSPRITEOFFSET] add $7 ld l, a ld a, [hl] ; c1x7 (counter until next walk animation frame) inc a ld [hl], a ; c1x7 += 1 cp $4 jr nz, .noNextAnimationFrame xor a ld [hl], a ; c1x7 = 0 inc l ld a, [hl] ; c1x8 (walk animation frame) inc a and $3 ld [hl], a ; advance to next animation frame every 4 ticks (16 ticks total for one step) .noNextAnimationFrame ld a, [H_CURRENTSPRITEOFFSET] add $3 ld l, a ld a, [hli] ; c1x3 (movement Y delta) ld b, a ld a, [hl] ; c1x4 (screen Y position) add b ld [hli], a ; update screen Y position ld a, [hli] ; c1x5 (movement X delta) ld b, a ld a, [hl] ; c1x6 (screen X position) add b ld [hl], a ; update screen X position ld a, [H_CURRENTSPRITEOFFSET] ld l, a inc h ld a, [hl] ; c2x0 (walk animantion counter) dec a ld [hl], a ; update walk animantion counter ret nz ld a, $6 ; walking finished, update state add l ld l, a ld a, [hl] ; c2x6 (movement byte 1) cp $fe jr nc, .initNextMovementCounter ; values $fe and $ff ld a, [H_CURRENTSPRITEOFFSET] inc a ld l, a dec h ld [hl], $1 ; c1x1 = 1 (movement status ready) ret .initNextMovementCounter call Random ld a, [H_CURRENTSPRITEOFFSET] add $8 ld l, a ld a, [hRandomAdd] and $7f ld [hl], a ; c2x8: set next movement delay to a random value in [0,$7f] dec h ; note that value 0 actually makes the delay $100 (bug?) ld a, [H_CURRENTSPRITEOFFSET] inc a ld l, a ld [hl], $2 ; c1x1 = 2 (movement status) inc l inc l xor a ld b, [hl] ; c1x3 (movement Y delta) ld [hli], a ; reset movement Y delta inc l ld c, [hl] ; c1x5 (movement X delta) ld [hl], a ; reset movement X delta ret ; update delay value (c2x8) for sprites in the delayed state (c1x1) UpdateSpriteMovementDelay: ; 5057 (1:5057) ld h, $c2 ld a, [H_CURRENTSPRITEOFFSET] add $6 ld l, a ld a, [hl] ; c2x6: movement byte 1 inc l inc l cp $fe jr nc, .tickMoveCounter ; values $fe or $ff ld [hl], $0 jr .moving .tickMoveCounter dec [hl] ; c2x8: frame counter until next movement jr nz, notYetMoving .moving dec h ld a, [H_CURRENTSPRITEOFFSET] inc a ld l, a ld [hl], $1 ; c1x1 = 1 (mark as ready to move) notYetMoving: ; 5073 (1:5073) ld h, $c1 ld a, [H_CURRENTSPRITEOFFSET] add $8 ld l, a ld [hl], $0 ; c1x8 = 0 (walk animation frame) jp UpdateSpriteImage InitializeSpriteFacingDirection: ; 507f (1:507f) ld a, [wd72d] bit 5, a jr nz, notYetMoving res 7, [hl] ld a, [wd52a] bit 3, a jr z, .notFacingDown ld c, $0 ; make sprite face down jr .facingDirectionDetermined .notFacingDown bit 2, a jr z, .notFacingUp ld c, $4 ; make sprite face up jr .facingDirectionDetermined .notFacingUp bit 1, a jr z, .notFacingRight ld c, $c ; make sprite face right jr .facingDirectionDetermined .notFacingRight ld c, $8 ; make sprite face left .facingDirectionDetermined ld a, [H_CURRENTSPRITEOFFSET] add $9 ld l, a ld [hl], c ; c1x9: set facing direction jr notYetMoving InitializeSpriteStatus: ; 50ad (1:50ad) ld [hl], $1 ; $c1x1: set movement status to ready inc l ld [hl], $ff ; $c1x2: set sprite image to $ff (invisible/off screen) inc h ld a, [H_CURRENTSPRITEOFFSET] add $2 ld l, a ld a, $8 ld [hli], a ; $c2x2: set Y displacement to 8 ld [hl], a ; $c2x3: set X displacement to 8 ret ; calculates the spprite's scrren position form its map position and the player position InitializeSpriteScreenPosition: ; 50bd (1:50bd) ld h, $c2 ld a, [H_CURRENTSPRITEOFFSET] add $4 ld l, a ld a, [W_YCOORD] ld b, a ld a, [hl] ; c2x4 (Y position + 4) sub b ; relative to player position swap a ; * 16 sub $4 ; - 4 dec h ld [hli], a ; c1x4 (screen Y position) inc h ld a, [W_XCOORD] ld b, a ld a, [hli] ; c2x6 (X position + 4) sub b ; relative to player position swap a ; * 16 dec h ld [hl], a ; c1x6 (screen X position) ret ; tests if sprite is off screen or otherwise unable to do anything CheckSpriteAvailability: ; 50dc (1:50dc) predef IsObjectHidden ld a, [$ffe5] and a jp nz, .spriteInvisible ld h, $c2 ld a, [H_CURRENTSPRITEOFFSET] add $6 ld l, a ld a, [hl] ; c2x6: movement byte 1 cp $fe jr c, .skipXVisibilityTest ; movement byte 1 < $fe (i.e. the sprite's movement is scripted) ld a, [H_CURRENTSPRITEOFFSET] add $4 ld l, a ld b, [hl] ; c2x4: Y pos (+4) ld a, [W_YCOORD] cp b jr z, .skipYVisibilityTest jr nc, .spriteInvisible ; above screen region add $8 ; screen is 9 tiles high cp b jr c, .spriteInvisible ; below screen region .skipYVisibilityTest inc l ld b, [hl] ; c2x5: X pos (+4) ld a, [W_XCOORD] cp b jr z, .skipXVisibilityTest jr nc, .spriteInvisible ; left of screen region add $9 ; screen is 10 tiles wide cp b jr c, .spriteInvisible ; right of screen region .skipXVisibilityTest ; make the sprite invisible if a text box is in front of it ; $5F is the maximum number for map tiles call GetTileSpriteStandsOn ld d, $60 ld a, [hli] cp d jr nc, .spriteInvisible ; standing on tile with ID >=$60 (bottom left tile) ld a, [hld] cp d jr nc, .spriteInvisible ; standing on tile with ID >=$60 (bottom right tile) ld bc, -20 add hl, bc ; go back one row of tiles ld a, [hli] cp d jr nc, .spriteInvisible ; standing on tile with ID >=$60 (top left tile) ld a, [hl] cp d jr c, .spriteVisible ; standing on tile with ID >=$60 (top right tile) .spriteInvisible ld h, $c1 ld a, [H_CURRENTSPRITEOFFSET] add $2 ld l, a ld [hl], $ff ; c1x2 scf jr .done .spriteVisible ld c, a ld a, [wWalkCounter] and a jr nz, .done ; if player is currently walking, we're done call UpdateSpriteImage inc h ld a, [H_CURRENTSPRITEOFFSET] add $7 ld l, a ld a, [W_GRASSTILE] cp c ld a, $0 jr nz, .notInGrass ld a, $80 .notInGrass ld [hl], a ; c2x7 and a .done ret UpdateSpriteImage: ; 5157 (1:5157) ld h, $c1 ld a, [H_CURRENTSPRITEOFFSET] add $8 ld l, a ld a, [hli] ; c1x8: walk animation frame ld b, a ld a, [hl] ; c1x9: facing direction add b ld b, a ld a, [$ff93] ; current sprite offset add b ld b, a ld a, [H_CURRENTSPRITEOFFSET] add $2 ld l, a ld [hl], b ; c1x2: sprite to display ret ; tests if sprite can walk the specified direction ; b: direction (1,2,4 or 8) ; c: ID of tile the sprite would walk onto ; d: Y movement delta (-1, 0 or 1) ; e: X movement delta (-1, 0 or 1) ; set carry on failure, clears carry on success CanWalkOntoTile: ; 516e (1:516e) ld h, $c2 ld a, [H_CURRENTSPRITEOFFSET] add $6 ld l, a ld a, [hl] ; c2x6 (movement byte 1) cp $fe jr nc, .notScripted ; values $fe and $ff ; always allow walking if the movement is scripted and a ret .notScripted ld a, [W_TILESETCOLLISIONPTR] ld l, a ld a, [W_TILESETCOLLISIONPTR+1] ld h, a .tilePassableLoop ld a, [hli] cp $ff jr z, .impassable cp c jr nz, .tilePassableLoop ld h, $c2 ld a, [H_CURRENTSPRITEOFFSET] add $6 ld l, a ld a, [hl] ; $c2x6 (movement byte 1) inc a jr z, .impassable ; if $ff, no movement allowed (however, changing direction is) ld h, $c1 ld a, [H_CURRENTSPRITEOFFSET] add $4 ld l, a ld a, [hli] ; c1x4 (screen Y pos) add $4 ; align to blocks (Y pos is always 4 pixels off) add d ; add Y delta cp $80 ; if value is >$80, the destination is off screen (either $81 or $FF underflow) jr nc, .impassable ; don't walk off screen inc l ld a, [hl] ; c1x6 (screen X pos) add e ; add X delta cp $90 ; if value is >$90, the destination is off screen (either $91 or $FF underflow) jr nc, .impassable ; don't walk off screen push de push bc call DetectCollisionBetweenSprites pop bc pop de ld h, $c1 ld a, [H_CURRENTSPRITEOFFSET] add $c ld l, a ld a, [hl] ; c1xc (directions in which sprite collision would occur) and b ; check against chosen direction (1,2,4 or 8) jr nz, .impassable ; collision between sprites, don't go there ld h, $c2 ld a, [H_CURRENTSPRITEOFFSET] add $2 ld l, a ld a, [hli] ; c2x2 (sprite Y displacement, initialized at $8, keep track of where a sprite did go) bit 7, d ; check if going upwards (d=$ff) jr nz, .upwards add d cp $5 jr c, .impassable ; if c2x2+d < 5, don't go ;bug: this tests probably were supposed to prevent sprites jr .checkHorizontal ; from walking out too far, but this line makes sprites get stuck .upwards ; whenever they walked upwards 5 steps sub $1 ; on the other hand, the amount a sprite can walk out to the jr c, .impassable ; if d2x2 == 0, don't go ; right of bottom is not limited (until the counter overflows) .checkHorizontal ld d, a ld a, [hl] ; c2x3 (sprite X displacement, initialized at $8, keep track of where a sprite did go) bit 7, e ; check if going left (e=$ff) jr nz, .left add e cp $5 ; compare, but no conditional jump like in the vertical check above (bug?) jr .passable .left sub $1 jr c, .impassable ; if d2x3 == 0, don't go .passable ld [hld], a ; update c2x3 ld [hl], d ; update c2x2 and a ; clear carry (marking success) ret .impassable ld h, $c1 ld a, [H_CURRENTSPRITEOFFSET] inc a ld l, a ld [hl], $2 ; c1x1 = 2 (set movement status to delayed) inc l inc l xor a ld [hli], a ; c1x3 = 0 (clear Y movement delta) inc l ld [hl], a ; c1x5 = 0 (clear X movement delta) inc h ld a, [H_CURRENTSPRITEOFFSET] add $8 ld l, a call Random ld a, [hRandomAdd] and $7f ld [hl], a ; c2x8: set next movement delay to a random value in [0,$7f] (again with delay $100 if value is 0) scf ; set carry (marking failure to walk) ret ; calculates the tile pointer pointing to the tile the current sprite stancs on ; this is always the lower left tile of the 2x2 tile blocks all sprites are snapped to ; hl: output pointer GetTileSpriteStandsOn: ; 5207 (1:5207) ld h, $c1 ld a, [H_CURRENTSPRITEOFFSET] add $4 ld l, a ld a, [hli] ; c1x4: screen Y position add $4 ; align to 2*2 tile blocks (Y position is always off 4 pixels to the top) and $f0 ; in case object is currently moving srl a ; screen Y tile * 4 ld c, a ld b, $0 inc l ld a, [hl] ; c1x6: screen Y position srl a srl a srl a ; screen X tile add SCREEN_WIDTH ; screen X tile + 20 ld d, $0 ld e, a hlCoord 0, 0 add hl, bc add hl, bc add hl, bc add hl, bc add hl, bc add hl, de ; wTileMap + 20*(screen Y tile + 1) + screen X tile ret ; loads [de+a] into a LoadDEPlusA: ; 522f (1:522f) add e ld e, a jr nc, .noCarry inc d .noCarry ld a, [de] ret DoScriptedNPCMovement: ; 5236 (1:5236) ; This is an alternative method of scripting an NPC's movement and is only used ; a few times in the game. It is used when the NPC and player must walk together ; in sync, such as when the player is following the NPC somewhere. An NPC can't ; be moved in sync with the player using the other method. ld a, [wd730] bit 7, a ret z ld hl, wd72e bit 7, [hl] set 7, [hl] jp z, InitScriptedNPCMovement ld hl, wNPCMovementDirections2 ld a, [wNPCMovementDirections2Index] add l ld l, a jr nc, .noCarry inc h .noCarry ld a, [hl] ; check if moving up cp NPC_MOVEMENT_UP jr nz, .checkIfMovingDown call GetSpriteScreenYPointer ld c, SPRITE_FACING_UP ld a, -2 jr .move .checkIfMovingDown cp NPC_MOVEMENT_DOWN jr nz, .checkIfMovingLeft call GetSpriteScreenYPointer ld c, SPRITE_FACING_DOWN ld a, 2 jr .move .checkIfMovingLeft cp NPC_MOVEMENT_LEFT jr nz, .checkIfMovingRight call GetSpriteScreenXPointer ld c, SPRITE_FACING_LEFT ld a, -2 jr .move .checkIfMovingRight cp NPC_MOVEMENT_RIGHT jr nz, .noMatch call GetSpriteScreenXPointer ld c, SPRITE_FACING_RIGHT ld a, 2 jr .move .noMatch cp $ff ret .move ld b, a ld a, [hl] add b ld [hl], a ld a, [H_CURRENTSPRITEOFFSET] add $9 ld l, a ld a, c ld [hl], a ; facing direction call AnimScriptedNPCMovement ld hl, wScriptedNPCWalkCounter dec [hl] ret nz ld a, 8 ld [wScriptedNPCWalkCounter], a ld hl, wNPCMovementDirections2Index inc [hl] ret InitScriptedNPCMovement: ; 52a6 (1:52a6) xor a ld [wNPCMovementDirections2Index], a ld a, 8 ld [wScriptedNPCWalkCounter], a jp AnimScriptedNPCMovement GetSpriteScreenYPointer: ; 52b2 (1:52b2) ld a, $4 ld b, a jr GetSpriteScreenXYPointerCommon GetSpriteScreenXPointer: ; 52b7 (1:52b7) ld a, $6 ld b, a GetSpriteScreenXYPointerCommon: ; 52ba (1:52ba) ld hl, wSpriteStateData1 ld a, [H_CURRENTSPRITEOFFSET] add l add b ld l, a ret AnimScriptedNPCMovement: ; 52c3 (1:52c3) ld hl, wSpriteStateData2 ld a, [H_CURRENTSPRITEOFFSET] add $e ld l, a ld a, [hl] ; VRAM slot dec a swap a ld b, a ld hl, wSpriteStateData1 ld a, [H_CURRENTSPRITEOFFSET] add $9 ld l, a ld a, [hl] ; facing direction cp SPRITE_FACING_DOWN jr z, .anim cp SPRITE_FACING_UP jr z, .anim cp SPRITE_FACING_LEFT jr z, .anim cp SPRITE_FACING_RIGHT jr z, .anim ret .anim add b ld b, a ld [hSpriteVRAMSlotAndFacing], a call AdvanceScriptedNPCAnimFrameCounter ld hl, wSpriteStateData1 ld a, [H_CURRENTSPRITEOFFSET] add $2 ld l, a ld a, [hSpriteVRAMSlotAndFacing] ld b, a ld a, [hSpriteAnimFrameCounter] add b ld [hl], a ret AdvanceScriptedNPCAnimFrameCounter: ; 5301 (1:5301) ld a, [H_CURRENTSPRITEOFFSET] add $7 ld l, a ld a, [hl] ; intra-animation frame counter inc a ld [hl], a cp 4 ret nz xor a ld [hl], a ; reset intra-animation frame counter inc l ld a, [hl] ; animation frame counter inc a and $3 ld [hl], a ld [hSpriteAnimFrameCounter], a ret