Merge pull request #256 from Rangi42/master

Add subdirectories to engine/ similar to pokecrystal

14 files changed, 891 insertions, 0 deletions

diff --git a/engine/battle/move_effects/conversion.asm b/engine/battle/move_effects/conversion.asm
new file mode 100644
index 00000000..f23c3d70
--- /dev/null
+++ b/engine/battle/move_effects/conversion.asm
@@ -0,0 +1,35 @@
+ConversionEffect_:
+	ld hl, wEnemyMonType1
+	ld de, wBattleMonType1
+	ld a, [H_WHOSETURN]
+	and a
+	ld a, [wEnemyBattleStatus1]
+	jr z, .conversionEffect
+	push hl
+	ld h, d
+	ld l, e
+	pop de
+	ld a, [wPlayerBattleStatus1]
+.conversionEffect
+	bit INVULNERABLE, a ; is mon immune to typical attacks (dig/fly)
+	jr nz, PrintButItFailedText
+; copy target's types to user
+	ld a, [hli]
+	ld [de], a
+	inc de
+	ld a, [hl]
+	ld [de], a
+	ld hl, PlayCurrentMoveAnimation
+	call CallBankF
+	ld hl, ConvertedTypeText
+	jp PrintText
+
+ConvertedTypeText:
+	TX_FAR _ConvertedTypeText
+	db "@"
+
+PrintButItFailedText:
+	ld hl, PrintButItFailedText_
+CallBankF:
+	ld b, BANK(PrintButItFailedText_)
+	jp Bankswitch
diff --git a/engine/battle/move_effects/drain_hp.asm b/engine/battle/move_effects/drain_hp.asm
new file mode 100644
index 00000000..e5f4681a
--- /dev/null
+++ b/engine/battle/move_effects/drain_hp.asm
@@ -0,0 +1,104 @@
+DrainHPEffect_:
+	ld hl, wDamage
+	ld a, [hl]
+	srl a ; divide damage by 2
+	ld [hli], a
+	ld a, [hl]
+	rr a
+	ld [hld], a
+	or [hl] ; is damage 0?
+	jr nz, .getAttackerHP
+; if damage is 0, increase to 1 so that the attacker gains at least 1 HP
+	inc hl
+	inc [hl]
+.getAttackerHP
+	ld hl, wBattleMonHP
+	ld de, wBattleMonMaxHP
+	ld a, [H_WHOSETURN]
+	and a
+	jp z, .addDamageToAttackerHP
+	ld hl, wEnemyMonHP
+	ld de, wEnemyMonMaxHP
+.addDamageToAttackerHP
+	ld bc, wHPBarOldHP+1
+; copy current HP to wHPBarOldHP
+	ld a, [hli]
+	ld [bc], a
+	ld a, [hl]
+	dec bc
+	ld [bc], a
+; copy max HP to wHPBarMaxHP
+	ld a, [de]
+	dec bc
+	ld [bc], a
+	inc de
+	ld a, [de]
+	dec bc
+	ld [bc], a
+; add damage to attacker's HP and copy new HP to wHPBarNewHP
+	ld a, [wDamage + 1]
+	ld b, [hl]
+	add b
+	ld [hld], a
+	ld [wHPBarNewHP], a
+	ld a, [wDamage]
+	ld b, [hl]
+	adc b
+	ld [hli], a
+	ld [wHPBarNewHP+1], a
+	jr c, .capToMaxHP ; if HP > 65,535, cap to max HP
+; compare HP with max HP
+	ld a, [hld]
+	ld b, a
+	ld a, [de]
+	dec de
+	sub b
+	ld a, [hli]
+	ld b, a
+	ld a, [de]
+	inc de
+	sbc b
+	jr nc, .next
+.capToMaxHP
+	ld a, [de]
+	ld [hld], a
+	ld [wHPBarNewHP], a
+	dec de
+	ld a, [de]
+	ld [hli], a
+	ld [wHPBarNewHP+1], a
+	inc de
+.next
+	ld a, [H_WHOSETURN]
+	and a
+	coord hl, 10, 9
+	ld a, $1
+	jr z, .next2
+	coord hl, 2, 2
+	xor a
+.next2
+	ld [wHPBarType], a
+	predef UpdateHPBar2
+	predef DrawPlayerHUDAndHPBar
+	predef DrawEnemyHUDAndHPBar
+	callab ReadPlayerMonCurHPAndStatus
+	ld hl, SuckedHealthText
+	ld a, [H_WHOSETURN]
+	and a
+	ld a, [wPlayerMoveEffect]
+	jr z, .next3
+	ld a, [wEnemyMoveEffect]
+.next3
+	cp DREAM_EATER_EFFECT
+	jr nz, .printText
+	ld hl, DreamWasEatenText
+.printText
+	jp PrintText
+
+SuckedHealthText:
+	TX_FAR _SuckedHealthText
+	db "@"
+
+DreamWasEatenText:
+	TX_FAR _DreamWasEatenText
+	db "@"
diff --git a/engine/battle/move_effects/focus_energy.asm b/engine/battle/move_effects/focus_energy.asm
new file mode 100644
index 00000000..16dad7bb
--- /dev/null
+++ b/engine/battle/move_effects/focus_energy.asm
@@ -0,0 +1,22 @@
+FocusEnergyEffect_:
+	ld hl, wPlayerBattleStatus2
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .notEnemy
+	ld hl, wEnemyBattleStatus2
+.notEnemy
+	bit GETTING_PUMPED, [hl] ; is mon already using focus energy?
+	jr nz, .alreadyUsing
+	set GETTING_PUMPED, [hl] ; mon is now using focus energy
+	callab PlayCurrentMoveAnimation
+	ld hl, GettingPumpedText
+	jp PrintText
+.alreadyUsing
+	ld c, 50
+	call DelayFrames
+	jpab PrintButItFailedText_
+
+GettingPumpedText:
+	TX_DELAY
+	TX_FAR _GettingPumpedText
+	db "@"
diff --git a/engine/battle/move_effects/haze.asm b/engine/battle/move_effects/haze.asm
new file mode 100644
index 00000000..47723ba2
--- /dev/null
+++ b/engine/battle/move_effects/haze.asm
@@ -0,0 +1,81 @@
+HazeEffect_:
+	ld a, $7
+; store 7 on every stat mod
+	ld hl, wPlayerMonAttackMod
+	call ResetStatMods
+	ld hl, wEnemyMonAttackMod
+	call ResetStatMods
+; copy unmodified stats to battle stats
+	ld hl, wPlayerMonUnmodifiedAttack
+	ld de, wBattleMonAttack
+	call ResetStats
+	ld hl, wEnemyMonUnmodifiedAttack
+	ld de, wEnemyMonAttack
+	call ResetStats
+; cure non-volatile status, but only for the target
+	ld hl, wEnemyMonStatus
+	ld de, wEnemySelectedMove
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .cureStatuses
+	ld hl, wBattleMonStatus
+	dec de ; wPlayerSelectedMove
+
+.cureStatuses
+	ld a, [hl]
+	ld [hl], $0
+	and SLP | (1 << FRZ)
+	jr z, .cureVolatileStatuses
+; prevent the Pokemon from executing a move if it was asleep or frozen
+	ld a, $ff
+	ld [de], a
+
+.cureVolatileStatuses
+	xor a
+	ld [wPlayerDisabledMove], a
+	ld [wEnemyDisabledMove], a
+	ld hl, wPlayerDisabledMoveNumber
+	ld [hli], a
+	ld [hl], a
+	ld hl, wPlayerBattleStatus1
+	call CureVolatileStatuses
+	ld hl, wEnemyBattleStatus1
+	call CureVolatileStatuses
+	ld hl, PlayCurrentMoveAnimation
+	call CallBankF
+	ld hl, StatusChangesEliminatedText
+	jp PrintText
+
+CureVolatileStatuses:
+	res CONFUSED, [hl]
+	inc hl ; BATTSTATUS2
+	ld a, [hl]
+	; clear USING_X_ACCURACY, PROTECTED_BY_MIST, GETTING_PUMPED, and SEEDED statuses
+	and $ff ^((1 << USING_X_ACCURACY) | (1 << PROTECTED_BY_MIST) | (1 << GETTING_PUMPED) | (1 << SEEDED))
+	ld [hli], a ; BATTSTATUS3
+	ld a, [hl]
+	and %11110000 | (1 << TRANSFORMED) ; clear Bad Poison, Reflect and Light Screen statuses
+	ld [hl], a
+	ret
+
+ResetStatMods:
+	ld b, $8
+.loop
+	ld [hli], a
+	dec b
+	jr nz, .loop
+	ret
+
+ResetStats:
+	ld b, $8
+.loop
+	ld a, [hli]
+	ld [de], a
+	inc de
+	dec b
+	jr nz, .loop
+	ret
+
+StatusChangesEliminatedText:
+	TX_FAR _StatusChangesEliminatedText
+	db "@"
diff --git a/engine/battle/move_effects/heal.asm b/engine/battle/move_effects/heal.asm
new file mode 100644
index 00000000..2e68acc0
--- /dev/null
+++ b/engine/battle/move_effects/heal.asm
@@ -0,0 +1,120 @@
+HealEffect_:
+	ld a, [H_WHOSETURN]
+	and a
+	ld de, wBattleMonHP
+	ld hl, wBattleMonMaxHP
+	ld a, [wPlayerMoveNum]
+	jr z, .healEffect
+	ld de, wEnemyMonHP
+	ld hl, wEnemyMonMaxHP
+	ld a, [wEnemyMoveNum]
+.healEffect
+	ld b, a
+	ld a, [de]
+	cp [hl] ; most significant bytes comparison is ignored
+	        ; causes the move to miss if max HP is 255 or 511 points higher than the current HP
+	inc de
+	inc hl
+	ld a, [de]
+	sbc [hl]
+	jp z, .failed ; no effect if user's HP is already at its maximum
+	ld a, b
+	cp REST
+	jr nz, .healHP
+	push hl
+	push de
+	push af
+	ld c, 50
+	call DelayFrames
+	ld hl, wBattleMonStatus
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .restEffect
+	ld hl, wEnemyMonStatus
+.restEffect
+	ld a, [hl]
+	and a
+	ld [hl], 2 ; clear status and set number of turns asleep to 2
+	ld hl, StartedSleepingEffect ; if mon didn't have an status
+	jr z, .printRestText
+	ld hl, FellAsleepBecameHealthyText ; if mon had an status
+.printRestText
+	call PrintText
+	pop af
+	pop de
+	pop hl
+.healHP
+	ld a, [hld]
+	ld [wHPBarMaxHP], a
+	ld c, a
+	ld a, [hl]
+	ld [wHPBarMaxHP+1], a
+	ld b, a
+	jr z, .gotHPAmountToHeal
+; Recover and Softboiled only heal for half the mon's max HP
+	srl b
+	rr c
+.gotHPAmountToHeal
+; update HP
+	ld a, [de]
+	ld [wHPBarOldHP], a
+	add c
+	ld [de], a
+	ld [wHPBarNewHP], a
+	dec de
+	ld a, [de]
+	ld [wHPBarOldHP+1], a
+	adc b
+	ld [de], a
+	ld [wHPBarNewHP+1], a
+	inc hl
+	inc de
+	ld a, [de]
+	dec de
+	sub [hl]
+	dec hl
+	ld a, [de]
+	sbc [hl]
+	jr c, .playAnim
+; copy max HP to current HP if an overflow occurred
+	ld a, [hli]
+	ld [de], a
+	ld [wHPBarNewHP+1], a
+	inc de
+	ld a, [hl]
+	ld [de], a
+	ld [wHPBarNewHP], a
+.playAnim
+	ld hl, PlayCurrentMoveAnimation
+	call BankswitchEtoF
+	ld a, [H_WHOSETURN]
+	and a
+	coord hl, 10, 9
+	ld a, $1
+	jr z, .updateHPBar
+	coord hl, 2, 2
+	xor a
+.updateHPBar
+	ld [wHPBarType], a
+	predef UpdateHPBar2
+	ld hl, DrawHUDsAndHPBars
+	call BankswitchEtoF
+	ld hl, RegainedHealthText
+	jp PrintText
+.failed
+	ld c, 50
+	call DelayFrames
+	ld hl, PrintButItFailedText_
+	jp BankswitchEtoF
+
+StartedSleepingEffect:
+	TX_FAR _StartedSleepingEffect
+	db "@"
+
+FellAsleepBecameHealthyText:
+	TX_FAR _FellAsleepBecameHealthyText
+	db "@"
+
+RegainedHealthText:
+	TX_FAR _RegainedHealthText
+	db "@"
diff --git a/engine/battle/move_effects/leech_seed.asm b/engine/battle/move_effects/leech_seed.asm
new file mode 100644
index 00000000..f4d3ee9c
--- /dev/null
+++ b/engine/battle/move_effects/leech_seed.asm
@@ -0,0 +1,40 @@
+LeechSeedEffect_:
+	callab MoveHitTest
+	ld a, [wMoveMissed]
+	and a
+	jr nz, .moveMissed
+	ld hl, wEnemyBattleStatus2
+	ld de, wEnemyMonType1
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .leechSeedEffect
+	ld hl, wPlayerBattleStatus2
+	ld de, wBattleMonType1
+.leechSeedEffect
+; miss if the target is grass-type or already seeded
+	ld a, [de]
+	cp GRASS
+	jr z, .moveMissed
+	inc de
+	ld a, [de]
+	cp GRASS
+	jr z, .moveMissed
+	bit SEEDED, [hl]
+	jr nz, .moveMissed
+	set SEEDED, [hl]
+	callab PlayCurrentMoveAnimation
+	ld hl, WasSeededText
+	jp PrintText
+.moveMissed
+	ld c, 50
+	call DelayFrames
+	ld hl, EvadedAttackText
+	jp PrintText
+
+WasSeededText:
+	TX_FAR _WasSeededText
+	db "@"
+
+EvadedAttackText:
+	TX_FAR _EvadedAttackText
+	db "@"
diff --git a/engine/battle/move_effects/mist.asm b/engine/battle/move_effects/mist.asm
new file mode 100644
index 00000000..65070a3e
--- /dev/null
+++ b/engine/battle/move_effects/mist.asm
@@ -0,0 +1,19 @@
+MistEffect_:
+	ld hl, wPlayerBattleStatus2
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .mistEffect
+	ld hl, wEnemyBattleStatus2
+.mistEffect
+	bit PROTECTED_BY_MIST, [hl] ; is mon protected by mist?
+	jr nz, .mistAlreadyInUse
+	set PROTECTED_BY_MIST, [hl] ; mon is now protected by mist
+	callab PlayCurrentMoveAnimation
+	ld hl, ShroudedInMistText
+	jp PrintText
+.mistAlreadyInUse
+	jpab PrintButItFailedText_
+
+ShroudedInMistText:
+	TX_FAR _ShroudedInMistText
+	db "@"
diff --git a/engine/battle/move_effects/one_hit_ko.asm b/engine/battle/move_effects/one_hit_ko.asm
new file mode 100644
index 00000000..827e2197
--- /dev/null
+++ b/engine/battle/move_effects/one_hit_ko.asm
@@ -0,0 +1,38 @@
+OneHitKOEffect_:
+	ld hl, wDamage
+	xor a
+	ld [hli], a
+	ld [hl], a ; set the damage output to zero
+	dec a
+	ld [wCriticalHitOrOHKO], a
+	ld hl, wBattleMonSpeed + 1
+	ld de, wEnemyMonSpeed + 1
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .compareSpeed
+	ld hl, wEnemyMonSpeed + 1
+	ld de, wBattleMonSpeed + 1
+.compareSpeed
+; set damage to 65535 and OHKO flag is the user's current speed is higher than the target's
+	ld a, [de]
+	dec de
+	ld b, a
+	ld a, [hld]
+	sub b
+	ld a, [de]
+	ld b, a
+	ld a, [hl]
+	sbc b
+	jr c, .userIsSlower
+	ld hl, wDamage
+	ld a, $ff
+	ld [hli], a
+	ld [hl], a
+	ld a, $2
+	ld [wCriticalHitOrOHKO], a
+	ret
+.userIsSlower
+; keep damage at 0 and set move missed flag if target's current speed is higher instead
+	ld a, $1
+	ld [wMoveMissed], a
+	ret
diff --git a/engine/battle/move_effects/paralyze.asm b/engine/battle/move_effects/paralyze.asm
new file mode 100644
index 00000000..95979ae6
--- /dev/null
+++ b/engine/battle/move_effects/paralyze.asm
@@ -0,0 +1,47 @@
+ParalyzeEffect_:
+	ld hl, wEnemyMonStatus
+	ld de, wPlayerMoveType
+	ld a, [H_WHOSETURN]
+	and a
+	jp z, .next
+	ld hl, wBattleMonStatus
+	ld de, wEnemyMoveType
+.next
+	ld a, [hl]
+	and a ; does the target already have a status ailment?
+	jr nz, .didntAffect
+; check if the target is immune due to types
+	ld a, [de]
+	cp ELECTRIC
+	jr nz, .hitTest
+	ld b, h
+	ld c, l
+	inc bc
+	ld a, [bc]
+	cp GROUND
+	jr z, .doesntAffect
+	inc bc
+	ld a, [bc]
+	cp GROUND
+	jr z, .doesntAffect
+.hitTest
+	push hl
+	callab MoveHitTest
+	pop hl
+	ld a, [wMoveMissed]
+	and a
+	jr nz, .didntAffect
+	set PAR, [hl]
+	callab QuarterSpeedDueToParalysis
+	ld c, 30
+	call DelayFrames
+	callab PlayCurrentMoveAnimation
+	jpab PrintMayNotAttackText
+.didntAffect
+	ld c, 50
+	call DelayFrames
+	jpab PrintDidntAffectText
+.doesntAffect
+	ld c, 50
+	call DelayFrames
+	jpab PrintDoesntAffectText
diff --git a/engine/battle/move_effects/pay_day.asm b/engine/battle/move_effects/pay_day.asm
new file mode 100644
index 00000000..e5daf014
--- /dev/null
+++ b/engine/battle/move_effects/pay_day.asm
@@ -0,0 +1,45 @@
+PayDayEffect_:
+	xor a
+	ld hl, wcd6d
+	ld [hli], a
+	ld a, [H_WHOSETURN]
+	and a
+	ld a, [wBattleMonLevel]
+	jr z, .payDayEffect
+	ld a, [wEnemyMonLevel]
+.payDayEffect
+; level * 2
+	add a
+	ld [H_DIVIDEND + 3], a
+	xor a
+	ld [H_DIVIDEND], a
+	ld [H_DIVIDEND + 1], a
+	ld [H_DIVIDEND + 2], a
+; convert to BCD
+	ld a, 100
+	ld [H_DIVISOR], a
+	ld b, $4
+	call Divide
+	ld a, [H_QUOTIENT + 3]
+	ld [hli], a
+	ld a, [H_REMAINDER]
+	ld [H_DIVIDEND + 3], a
+	ld a, 10
+	ld [H_DIVISOR], a
+	ld b, $4
+	call Divide
+	ld a, [H_QUOTIENT + 3]
+	swap a
+	ld b, a
+	ld a, [H_REMAINDER]
+	add b
+	ld [hl], a
+	ld de, wTotalPayDayMoney + 2
+	ld c, $3
+	predef AddBCDPredef
+	ld hl, CoinsScatteredText
+	jp PrintText
+
+CoinsScatteredText:
+	TX_FAR _CoinsScatteredText
+	db "@"
diff --git a/engine/battle/move_effects/recoil.asm b/engine/battle/move_effects/recoil.asm
new file mode 100644
index 00000000..0f2f087b
--- /dev/null
+++ b/engine/battle/move_effects/recoil.asm
@@ -0,0 +1,70 @@
+RecoilEffect_:
+	ld a, [H_WHOSETURN]
+	and a
+	ld a, [wPlayerMoveNum]
+	ld hl, wBattleMonMaxHP
+	jr z, .recoilEffect
+	ld a, [wEnemyMoveNum]
+	ld hl, wEnemyMonMaxHP
+.recoilEffect
+	ld d, a
+	ld a, [wDamage]
+	ld b, a
+	ld a, [wDamage + 1]
+	ld c, a
+	srl b
+	rr c
+	ld a, d
+	cp STRUGGLE ; struggle deals 50% recoil damage
+	jr z, .gotRecoilDamage
+	srl b
+	rr c
+.gotRecoilDamage
+	ld a, b
+	or c
+	jr nz, .updateHP
+	inc c ; minimum recoil damage is 1
+.updateHP
+; subtract HP from user due to the recoil damage
+	ld a, [hli]
+	ld [wHPBarMaxHP+1], a
+	ld a, [hl]
+	ld [wHPBarMaxHP], a
+	push bc
+	ld bc, wBattleMonHP - wBattleMonMaxHP
+	add hl, bc
+	pop bc
+	ld a, [hl]
+	ld [wHPBarOldHP], a
+	sub c
+	ld [hld], a
+	ld [wHPBarNewHP], a
+	ld a, [hl]
+	ld [wHPBarOldHP+1], a
+	sbc b
+	ld [hl], a
+	ld [wHPBarNewHP+1], a
+	jr nc, .getHPBarCoords
+; if recoil damage is higher than the Pokemon's HP, set its HP to 0
+	xor a
+	ld [hli], a
+	ld [hl], a
+	ld hl, wHPBarNewHP
+	ld [hli], a
+	ld [hl], a
+.getHPBarCoords
+	coord hl, 10, 9
+	ld a, [H_WHOSETURN]
+	and a
+	ld a, $1
+	jr z, .updateHPBar
+	coord hl, 2, 2
+	xor a
+.updateHPBar
+	ld [wHPBarType], a
+	predef UpdateHPBar2
+	ld hl, HitWithRecoilText
+	jp PrintText
+HitWithRecoilText:
+	TX_FAR _HitWithRecoilText
+	db "@"
diff --git a/engine/battle/move_effects/reflect_light_screen.asm b/engine/battle/move_effects/reflect_light_screen.asm
new file mode 100644
index 00000000..2805a969
--- /dev/null
+++ b/engine/battle/move_effects/reflect_light_screen.asm
@@ -0,0 +1,45 @@
+ReflectLightScreenEffect_:
+	ld hl, wPlayerBattleStatus3
+	ld de, wPlayerMoveEffect
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .reflectLightScreenEffect
+	ld hl, wEnemyBattleStatus3
+	ld de, wEnemyMoveEffect
+.reflectLightScreenEffect
+	ld a, [de]
+	cp LIGHT_SCREEN_EFFECT
+	jr nz, .reflect
+	bit HAS_LIGHT_SCREEN_UP, [hl] ; is mon already protected by light screen?
+	jr nz, .moveFailed
+	set HAS_LIGHT_SCREEN_UP, [hl] ; mon is now protected by light screen
+	ld hl, LightScreenProtectedText
+	jr .playAnim
+.reflect
+	bit HAS_REFLECT_UP, [hl] ; is mon already protected by reflect?
+	jr nz, .moveFailed
+	set HAS_REFLECT_UP, [hl] ; mon is now protected by reflect
+	ld hl, ReflectGainedArmorText
+.playAnim
+	push hl
+	ld hl, PlayCurrentMoveAnimation
+	call BankswitchEtoF
+	pop hl
+	jp PrintText
+.moveFailed
+	ld c, 50
+	call DelayFrames
+	ld hl, PrintButItFailedText_
+	jp BankswitchEtoF
+
+LightScreenProtectedText:
+	TX_FAR _LightScreenProtectedText
+	db "@"
+
+ReflectGainedArmorText:
+	TX_FAR _ReflectGainedArmorText
+	db "@"
+
+BankswitchEtoF:
+	ld b, BANK(BattleCore)
+	jp Bankswitch
diff --git a/engine/battle/move_effects/substitute.asm b/engine/battle/move_effects/substitute.asm
new file mode 100644
index 00000000..1bb6c887
--- /dev/null
+++ b/engine/battle/move_effects/substitute.asm
@@ -0,0 +1,77 @@
+SubstituteEffect_:
+	ld c, 50
+	call DelayFrames
+	ld hl, wBattleMonMaxHP
+	ld de, wPlayerSubstituteHP
+	ld bc, wPlayerBattleStatus2
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .notEnemy
+	ld hl, wEnemyMonMaxHP
+	ld de, wEnemySubstituteHP
+	ld bc, wEnemyBattleStatus2
+.notEnemy
+	ld a, [bc]
+	bit HAS_SUBSTITUTE_UP, a ; user already has substitute?
+	jr nz, .alreadyHasSubstitute
+; quarter health to remove from user
+; assumes max HP is 1023 or lower
+	push bc
+	ld a, [hli]
+	ld b, [hl]
+	srl a
+	rr b
+	srl a
+	rr b ; max hp / 4
+	push de
+	ld de, wBattleMonHP - wBattleMonMaxHP
+	add hl, de ; point hl to current HP low byte
+	pop de
+	ld a, b
+	ld [de], a ; save copy of HP to subtract in wPlayerSubstituteHP/wEnemySubstituteHP
+	ld a, [hld]
+; subtract [max hp / 4] to current HP
+	sub b
+	ld d, a
+	ld a, [hl]
+	sbc 0
+	pop bc
+	jr c, .notEnoughHP ; underflow means user would be left with negative health
+                           ; bug: since it only branches on carry, it will possibly leave user with 0 HP
+.userHasZeroOrMoreHP
+	ldi [hl], a ; save resulting HP after subtraction into current HP
+	ld [hl], d
+	ld h, b
+	ld l, c
+	set HAS_SUBSTITUTE_UP, [hl]
+	ld a, [wOptions]
+	bit 7, a ; battle animation is enabled?
+	ld hl, PlayCurrentMoveAnimation
+	ld b, BANK(PlayCurrentMoveAnimation)
+	jr z, .animationEnabled
+	ld hl, AnimationSubstitute
+	ld b, BANK(AnimationSubstitute)
+.animationEnabled
+	call Bankswitch ; jump to routine depending on animation setting
+	ld hl, SubstituteText
+	call PrintText
+	jpab DrawHUDsAndHPBars
+.alreadyHasSubstitute
+	ld hl, HasSubstituteText
+	jr .printText
+.notEnoughHP
+	ld hl, TooWeakSubstituteText
+.printText
+	jp PrintText
+
+SubstituteText:
+	TX_FAR _SubstituteText
+	db "@"
+
+HasSubstituteText:
+	TX_FAR _HasSubstituteText
+	db "@"
+
+TooWeakSubstituteText:
+	TX_FAR _TooWeakSubstituteText
+	db "@"
diff --git a/engine/battle/move_effects/transform.asm b/engine/battle/move_effects/transform.asm
new file mode 100644
index 00000000..9a5de9cc
--- /dev/null
+++ b/engine/battle/move_effects/transform.asm
@@ -0,0 +1,148 @@
+TransformEffect_:
+	ld hl, wBattleMonSpecies
+	ld de, wEnemyMonSpecies
+	ld bc, wEnemyBattleStatus3
+	ld a, [wEnemyBattleStatus1]
+	ld a, [H_WHOSETURN]
+	and a
+	jr nz, .hitTest
+	ld hl, wEnemyMonSpecies
+	ld de, wBattleMonSpecies
+	ld bc, wPlayerBattleStatus3
+	ld [wPlayerMoveListIndex], a
+	ld a, [wPlayerBattleStatus1]
+.hitTest
+	bit INVULNERABLE, a ; is mon invulnerable to typical attacks? (fly/dig)
+	jp nz, .failed
+	push hl
+	push de
+	push bc
+	ld hl, wPlayerBattleStatus2
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .transformEffect
+	ld hl, wEnemyBattleStatus2
+.transformEffect
+; animation(s) played are different if target has Substitute up
+	bit HAS_SUBSTITUTE_UP, [hl]
+	push af
+	ld hl, HideSubstituteShowMonAnim
+	ld b, BANK(HideSubstituteShowMonAnim)
+	call nz, Bankswitch
+	ld a, [wOptions]
+	add a
+	ld hl, PlayCurrentMoveAnimation
+	ld b, BANK(PlayCurrentMoveAnimation)
+	jr nc, .gotAnimToPlay
+	ld hl, AnimationTransformMon
+	ld b, BANK(AnimationTransformMon)
+.gotAnimToPlay
+	call Bankswitch
+	ld hl, ReshowSubstituteAnim
+	ld b, BANK(ReshowSubstituteAnim)
+	pop af
+	call nz, Bankswitch
+	pop bc
+	ld a, [bc]
+	set TRANSFORMED, a ; mon is now transformed
+	ld [bc], a
+	pop de
+	pop hl
+	push hl
+; transform user into opposing Pokemon
+; species
+	ld a, [hl]
+	ld [de], a
+; type 1, type 2, catch rate, and moves
+	ld bc, $5
+	add hl, bc
+	inc de
+	inc de
+	inc de
+	inc de
+	inc de
+	inc bc
+	inc bc
+	call CopyData
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .next
+; save enemy mon DVs at wTransformedEnemyMonOriginalDVs
+	ld a, [de]
+	ld [wTransformedEnemyMonOriginalDVs], a
+	inc de
+	ld a, [de]
+	ld [wTransformedEnemyMonOriginalDVs + 1], a
+	dec de
+.next
+; DVs
+	ld a, [hli]
+	ld [de], a
+	inc de
+	ld a, [hli]
+	ld [de], a
+	inc de
+; Attack, Defense, Speed, and Special stats
+	inc hl
+	inc hl
+	inc hl
+	inc de
+	inc de
+	inc de
+	ld bc, $8
+	call CopyData
+	ld bc, wBattleMonMoves - wBattleMonPP
+	add hl, bc ; ld hl, wBattleMonMoves
+	ld b, NUM_MOVES
+.copyPPLoop
+; 5 PP for all moves
+	ld a, [hli]
+	and a
+	jr z, .lessThanFourMoves
+	ld a, $5
+	ld [de], a
+	inc de
+	dec b
+	jr nz, .copyPPLoop
+	jr .copyStats
+.lessThanFourMoves
+; 0 PP for blank moves
+	xor a
+	ld [de], a
+	inc de
+	dec b
+	jr nz, .lessThanFourMoves
+.copyStats
+; original (unmodified) stats and stat mods
+	pop hl
+	ld a, [hl]
+	ld [wd11e], a
+	call GetMonName
+	ld hl, wEnemyMonUnmodifiedAttack
+	ld de, wPlayerMonUnmodifiedAttack
+	call .copyBasedOnTurn ; original (unmodified) stats
+	ld hl, wEnemyMonStatMods
+	ld de, wPlayerMonStatMods
+	call .copyBasedOnTurn ; stat mods
+	ld hl, TransformedText
+	jp PrintText
+
+.copyBasedOnTurn
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .gotStatsOrModsToCopy
+	push hl
+	ld h, d
+	ld l, e
+	pop de
+.gotStatsOrModsToCopy
+	ld bc, $8
+	jp CopyData
+
+.failed
+	ld hl, PrintButItFailedText_
+	jp BankswitchEtoF
+
+TransformedText:
+	TX_FAR _TransformedText
+	db "@"