ref: 5e9de74735d09b2a43e8d1c6314f2a7839b6e55a
dir: /docs/bugs_and_glitches.md/
# Bugs and Glitches
These are known bugs and glitches in the original Pokémon Crystal game: code that clearly does not work as intended, or that only works in limited circumstances but has the possibility to fail or crash.
Fixes are written in the `diff` format. If you've used Git before, this should look familiar:
```diff
this is some code
-delete red - lines
+add green + lines
```
Some fixes are mentioned as breaking compatibility with link battles. This can be avoided by writing more complicated fixes that only apply if the value at `[wLinkMode]` is not `LINK_COLOSSEUM`. That's how Crystal itself fixed two bugs in Gold and Silver regarding the moves [Reflect and Light Screen](#reflect-and-light-screen-can-make-special-defense-wrap-around-above-1024) and [Present](#present-damage-is-incorrect-in-link-battles).
## Contents
- [Perish Song and Spikes can leave a Pokémon with 0 HP and not faint](#perish-song-and-spikes-can-leave-a-pokémon-with-0-hp-and-not-faint)
- [Thick Club and Light Ball can make (Special) Attack wrap around above 1024](#thick-club-and-light-ball-can-make-special-attack-wrap-around-above-1024)
- [Metal Powder can increase damage taken with boosted (Special) Defense](#metal-powder-can-increase-damage-taken-with-boosted-special-defense)
- [Reflect and Light Screen can make (Special) Defense wrap around above 1024](#reflect-and-light-screen-can-make-special-defense-wrap-around-above-1024)
- [Glacier Badge may not boost Special Defense depending on the value of Special Attack](#glacier-badge-may-not-boost-special-defense-depending-on-the-value-of-special-attack)
- [Moves with a 100% secondary effect chance will not trigger it in 1/256 uses](#moves-with-a-100-secondary-effect-chance-will-not-trigger-it-in-1256-uses)
- [Belly Drum sharply boosts Attack even with under 50% HP](#belly-drum-sharply-boosts-attack-even-with-under-50-hp)
- [Berserk Gene's confusion lasts for 256 turns or the previous Pokémon's confusion count](#berserk-genes-confusion-lasts-for-256-turns-or-the-previous-Pokémons-confusion-count)
- [Confusion damage is affected by type-boosting items and Explosion/Self-Destruct doubling](#confusion-damage-is-affected-by-type-boosting-items-and-explosionself-destruct-doubling)
- [Saves corrupted by mid-save shutoff are not handled](#saves-corrupted-by-mid-save-shutoff-are-not-handled)
- [Moves that lower Defense can do so after breaking a Substitute](#moves-that-lower-defense-can-do-so-after-breaking-a-substitute)
- [Counter and Mirror Coat still work if the opponent uses an item](#counter-and-mirror-coat-still-work-if-the-opponent-uses-an-item)
- [A Disabled but PP Up–enhanced move may not trigger Struggle](#a-disabled-but-pp-upenhanced-move-may-not-trigger-struggle)
- [A Pokémon that fainted from Pursuit will have its old status condition when revived](#a-pokémon-that-fainted-from-pursuit-will-have-its-old-status-condition-when-revived)
- [Lock-On and Mind Reader don't always bypass Fly and Dig](#lock-on-and-mind-reader-dont-always-bypass-fly-and-dig)
- [Wild Pokémon can always Teleport regardless of level difference](#wild-pokémon-can-always-teleport-regardless-of-level-difference)
- [Beat Up can desynchronize link battles](#beat-up-can-desynchronize-link-battles)
- [Beat Up works incorrectly with only one Pokémon in the party](#beat-up-works-incorrectly-with-only-one-pokémon-in-the-party)
- [Beat Up may fail to raise Substitute](#beat-up-may-fail-to-raise-substitute)
- [Beat Up may trigger King's Rock even if it failed](#beat-up-may-trigger-kings-rock-even-if-it-failed)
- [Present damage is incorrect in link battles](#present-damage-is-incorrect-in-link-battles)
- [A Transformed Pokémon can use Sketch and learn otherwise unobtainable moves](#a-transformed-pokémon-can-use-sketch-and-learn-otherwise-unobtainable-moves)
- ["Smart" AI encourages Mean Look if its own Pokémon is badly poisoned](#smart-ai-encourages-mean-look-if-its-own-pokémon-is-badly-poisoned)
- [AI makes a false assumption about `CheckTypeMatchup`](#ai-makes-a-false-assumption-about-checktypematchup)
- [NPC use of Full Heal or Full Restore does not cure Nightmare status](#npc-use-of-full-heal-or-full-restore-does-not-cure-nightmare-status)
- [NPC use of Full Heal does not cure confusion status](#npc-use-of-full-heal-does-not-cure-confusion-status)
- [HP bar animation is slow for high HP](#hp-bar-animation-is-slow-for-high-hp)
- [HP bar animation off-by-one error for low HP](#hp-bar-animation-off-by-one-error-for-low-hp)
- [Experience underflow for level 1 Pokémon with Medium-Slow growth rate](#experience-underflow-for-level-1-pokémon-with-medium-slow-growth-rate)
- [Five-digit experience gain is printed incorrectly](#five-digit-experience-gain-is-printed-incorrectly)
- [BRN/PSN/PAR do not affect catch rate](#brnpsnpar-do-not-affect-catch-rate)
- [Moon Ball does not boost catch rate](#moon-ball-does-not-boost-catch-rate)
- [Love Ball boosts catch rate for the wrong gender](#love-ball-boosts-catch-rate-for-the-wrong-gender)
- [Fast Ball only boosts catch rate for three Pokémon](#fast-ball-only-boosts-catch-rate-for-three-pokémon)
- [Dragon Scale, not Dragon Fang, boosts Dragon-type moves](#dragon-scale-not-dragon-fang-boosts-dragon-type-moves)
- [Clair can give TM24 Dragonbreath twice](#clair-can-give-tm24-dragonbreath-twice)
- [Daisy's grooming doesn't always increase happiness](#daisys-grooming-doesnt-always-increase-happiness)
- [Magikarp in Lake of Rage are shorter, not longer](#magikarp-in-lake-of-rage-are-shorter-not-longer)
- [Magikarp length limits have a unit conversion error](#magikarp-length-limits-have-a-unit-conversion-error)
- [Magikarp lengths can be miscalculated](#magikarp-lengths-can-be-miscalculated)
- [Battle transitions fail to account for the enemy's level](#battle-transitions-fail-to-account-for-the-enemys-level)
- [A "HOF Master!" title for 200-Time Famers is defined but inaccessible](#a-hof-master-title-for-200-time-famers-is-defined-but-inaccessible)
- [Slot machine payout sound effects cut each other off](#slot-machine-payout-sound-effects-cut-each-other-off)
- [Team Rocket battle music is not used for Executives or Scientists](#team-rocket-battle-music-is-not-used-for-executives-or-scientists)
- [No bump noise if standing on tile `$3E`](#no-bump-noise-if-standing-on-tile-3e)
- [Playing Entei's Pokédex cry can distort Raikou's and Suicune's](#playing-enteis-pokédex-cry-can-distort-raikous-and-suicunes)
- [In-battle “`…`” ellipsis is too high](#in-battle--ellipsis-is-too-high)
- [Move selection menu doesn't handle joypad properly](#move-selection-menu-doesnt-handle-joypad-properly)
- [Two tiles in the `port` tileset are drawn incorrectly](#two-tiles-in-the-port-tileset-are-drawn-incorrectly)
- [`LoadMetatiles` wraps around past 128 blocks](#loadmetatiles-wraps-around-past-128-blocks)
- [Surfing directly across a map connection does not load the new map](#surfing-directly-across-a-map-connection-does-not-load-the-new-map)
- [Swimming NPCs aren't limited by their movement radius](#swimming-npcs-arent-limited-by-their-movement-radius)
- [`CheckOwnMon` only checks the first five letters of OT names](#checkownmon-only-checks-the-first-five-letters-of-ot-names)
- [Catching a Transformed Pokémon always catches a Ditto](#catching-a-transformed-pokémon-always-catches-a-ditto)
- [If your party and current PC box are full during the Dude's catching tutorial, his Poké Ball can't be used and may crash the game](#if-your-party-and-current-pc-box-are-full-during-the-dudes-catching-tutorial-his-poké-ball-cant-be-used-and-may-crash-the-game)
- [Using a Park Ball in normal battles has a corrupt animation](#using-a-park-ball-in-normal-battles-has-a-corrupt-animation)
- [`HELD_CATCH_CHANCE` has no effect](#held_catch_chance-has-no-effect)
- [Only the first three evolution entries can have Stone compatibility reported correctly](#only-the-first-three-evolution-entries-can-have-stone-compatibility-reported-correctly)
- [`EVOLVE_STAT` can break Stone compatibility reporting](#evolve_stat-can-break-stone-compatibility-reporting)
- [`ScriptCall` can overflow `wScriptStack` and crash](#scriptcall-can-overflow-wscriptstack-and-crash)
- [`LoadSpriteGFX` does not limit the capacity of `UsedSprites`](#loadspritegfx-does-not-limit-the-capacity-of-usedsprites)
- [`ChooseWildEncounter` doesn't really validate the wild Pokémon species](#choosewildencounter-doesnt-really-validate-the-wild-pokémon-species)
- [`TryObjectEvent` arbitrary code execution](#tryobjectevent-arbitrary-code-execution)
- [`ReadObjectEvents` overflows into `wObjectMasks`](#readobjectevents-overflows-into-wobjectmasks)
- [`ClearWRAM` only clears WRAM bank 1](#clearwram-only-clears-wram-bank-1)
- [`BattleAnimCmd_ClearObjs` only clears the first 6⅔ objects](#battleanimcmd_clearobjs-only-clears-the-first-6-objects)
## Perish Song and Spikes can leave a Pokémon with 0 HP and not faint
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=1IiPWw5fMf8&t=85))
**Fix:** Edit `CheckFaint_PlayerThenEnemy` and `CheckFaint_EnemyThenPlayer` in [engine/battle/core.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/core.asm):
```diff
jp HandleEncore
+HasAnyoneFainted:
+ call HasPlayerFainted
+ jp nz, HasEnemyFainted
+ ret
+
CheckFaint_PlayerThenEnemy:
+.faint_loop
+ call .Function
+ ret c
+ call HasAnyoneFainted
+ ret nz
+ jr .faint_loop
+
+.Function:
call HasPlayerFainted
jr nz, .PlayerNotFainted
call HandlePlayerMonFaint
...
```
```diff
CheckFaint_EnemyThenPlayer:
+.faint_loop
+ call .Function
+ ret c
+ call HasAnyoneFainted
+ ret nz
+ jr .faint_loop
+
+.Function:
call HasEnemyFainted
jr nz, .EnemyNotFainted
call HandleEnemyMonFaint
...
```
## Thick Club and Light Ball can make (Special) Attack wrap around above 1024
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=rGqu3d3pdok&t=450))
**Fix:** Edit `SpeciesItemBoost` in [engine/battle/effect_commands.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/effect_commands.asm)
```diff
; Double the stat
sla l
rl h
+
+ ld a, HIGH(MAX_STAT_VALUE)
+ cp h
+ jr c, .cap
+ ret nz
+ ld a, LOW(MAX_STAT_VALUE)
+ cp l
+ ret nc
+
+.cap
+ ld hl, MAX_STAT_VALUE
ret
```
## Metal Powder can increase damage taken with boosted (Special) Defense
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=rGqu3d3pdok&t=450))
**Fix:** Edit `DittoMetalPowder` in [engine/battle/effect_commands.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/effect_commands.asm):
```diff
ld a, c
srl a
add c
ld c, a
ret nc
srl b
ld a, b
and a
jr nz, .done
inc b
.done
scf
rr c
+
+ ld a, HIGH(MAX_STAT_VALUE)
+ cp b
+ jr c, .cap
+ ret nz
+ ld a, LOW(MAX_STAT_VALUE)
+ cp c
+ ret nc
+
+.cap
+ ld bc, MAX_STAT_VALUE
ret
```
## Reflect and Light Screen can make (Special) Defense wrap around above 1024
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
This bug existed for all battles in Gold and Silver, and was only fixed for single-player battles in Crystal to preserve link compatibility.
**Fix:** Edit `TruncateHL_BC` in [engine/battle/effect_commands.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/effect_commands.asm)
```diff
.finish
- ld a, [wLinkMode]
- cp LINK_COLOSSEUM
- jr z, .done
; If we go back to the loop point,
; it's the same as doing this exact
; same check twice.
ld a, h
or b
jr nz, .loop
-.done
ld b, l
ret
```
(This fix also affects Thick Club, Light Ball, and Metal Powder, as described above, but their specific fixes in the above bugs allow more accurate damage calculations.)
## Glacier Badge may not boost Special Defense depending on the value of Special Attack
As Pryce's dialog ("That BADGE will raise the SPECIAL stats of POKéMON.") implies, Glacier Badge is intended to boost both Special Attack and Special Defense. However, due to BoostStat overwriting `a` when boosting Special Attack, the Special Defense boost will not happen if the unboosted Special Attack stat is either 0-205 or 433-660.
**Fix:** Edit `BadgeStatBoosts.CheckBadge` in [engine/battle/core.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/core.asm):
```diff
.CheckBadge:
ld a, b
srl b
+ push af
call c, BoostStat
+ pop af
inc hl
inc hl
; Check every other badge.
srl b
dec c
jr nz, .CheckBadge
; Check GlacierBadge again for Special Defense.
-; This check is buggy because it assumes that a is set by the "ld a, b" in the above loop,
-; but it can actually be overwritten by the call to BoostStat.
srl a
call c, BoostStat
ret
```
## Moves with a 100% secondary effect chance will not trigger it in 1/256 uses
*Fixing this bug **may** break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=mHkyO5T5wZU&t=206))
**Fix:** Edit `BattleCommand_EffectChance` in [engine/battle/effect_commands.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/effect_commands.asm):
```diff
- ; BUG: 1/256 chance to fail even for a 100% effect chance,
- ; since carry is not set if BattleRandom == [hl] == 255
- call BattleRandom
+ ld a, [hl]
+ sub 100 percent
+ ; If chance was 100%, RNG won't be called (carry not set)
+ ; Thus chance will be subtracted from 0, guaranteeing a carry
+ call c, BattleRandom
cp [hl]
pop hl
ret c
.failed
ld a, 1
ld [wEffectFailed], a
and a
ret
```
**Compatibility preservation:** If you wish to keep compatibility with standard Pokémon Crystal, you can disable the fix during link battles by also applying the following edit in the same place:
```diff
+ ld a, [wLinkMode]
+ cp LINK_COLOSSEUM
+ scf ; Force RNG to be called
+ jr z, .nofix ; Don't apply fix in link battles, for compatibility
ld a, [hl]
sub 100 percent
; If chance was 100%, RNG won't be called (carry not set)
; Thus chance will be subtracted from 0, guaranteeing a carry
+.nofix
call c, BattleRandom
```
## Belly Drum sharply boosts Attack even with under 50% HP
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=zuCLMikWo4Y))
**Fix:** Edit `BattleCommand_BellyDrum` in [engine/battle/move_effects/belly_drum.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/move_effects/belly_drum.asm):
```diff
BattleCommand_BellyDrum:
; bellydrum
-; This command is buggy because it raises the user's attack
-; before checking that it has enough HP to use the move.
-; Swap the order of these two blocks to fix.
- call BattleCommand_AttackUp2
- ld a, [wAttackMissed]
- and a
- jr nz, .failed
-
callfar GetHalfMaxHP
callfar CheckUserHasEnoughHP
jr nc, .failed
+
+ push bc
+ call BattleCommand_AttackUp2
+ pop bc
+ ld a, [wAttackMissed]
+ and a
+ jr nz, .failed
```
## Berserk Gene's confusion lasts for 256 turns or the previous Pokémon's confusion count
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://youtube.com/watch?v=Pru3mohq20A))
**Fix:** Edit `HandleBerserkGene` in [engine/battle/core.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/core.asm):
```diff
HandleBerserkGene:
...
ld a, BATTLE_VARS_SUBSTATUS3
call GetBattleVarAddr
push af
set SUBSTATUS_CONFUSED, [hl]
+ ldh a, [hBattleTurn]
+ and a
+ ld hl, wEnemyConfuseCount
+ jr z, .set_confuse_count
+ ld hl, wPlayerConfuseCount
+.set_confuse_count
+ call BattleRandom
+ and %11
+ add 2
+ ld [hl], a
ld a, BATTLE_VARS_MOVE_ANIM
call GetBattleVarAddr
...
```
This makes the Berserk Gene use the regular confusion duration (2-5 turns).
## Confusion damage is affected by type-boosting items and Explosion/Self-Destruct doubling
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://twitter.com/crystal_rby/status/874626362287562752))
**Fix:**
First, edit [wram.asm](https://github.com/pret/pokecrystal/blob/master/wram.asm):
```diff
wTurnEnded:: db ; c6b4
- ds 1
+wIsConfusionDamage:: db ; c6b5
wPlayerStats:: ; c6b6
```
Then edit four routines in [engine/battle/effect_commands.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/effect_commands.asm):
```diff
HitSelfInConfusion:
...
call TruncateHL_BC
ld d, 40
pop af
ld e, a
+ ld a, TRUE
+ ld [wIsConfusionDamage], a
ret
```
```diff
BattleCommand_DamageCalc:
; damagecalc
...
.skip_zero_damage_check
+ xor a ; Not confusion damage
+ ld [wIsConfusionDamage], a
+ ; fallthrough
+
+ConfusionDamageCalc:
; Minimum defense value is 1.
ld a, c
and a
jr nz, .not_dividing_by_zero
ld c, 1
.not_dividing_by_zero
...
; Item boosts
+
+; Item boosts don't apply to confusion damage
+ ld a, [wIsConfusionDamage]
+ and a
+ jr nz, .DoneItem
+
call GetUserItem
...
```
```diff
CheckEnemyTurn:
...
ld hl, HurtItselfText
call StdBattleTextbox
call HitSelfInConfusion
- call BattleCommand_DamageCalc
+ call ConfusionDamageCalc
call BattleCommand_LowerSub
...
```
```diff
HitConfusion:
ld hl, HurtItselfText
call StdBattleTextbox
xor a
ld [wCriticalHit], a
call HitSelfInConfusion
- call BattleCommand_DamageCalc
+ call ConfusionDamageCalc
call BattleCommand_LowerSub
```
## Saves corrupted by mid-save shutoff are not handled
([Video 1](https://www.youtube.com/watch?v=ukqtK0l6bu0), [Video 2](https://www.youtube.com/watch?v=c2zHd1BPtvc))
**Fix:** Edit `MoveMonWOMail_InsertMon_SaveGame` and `_SaveGameData` in [engine/menus/save.asm](https://github.com/pret/pokecrystal/blob/master/engine/menus/save.asm):
```diff
MoveMonWOMail_InsertMon_SaveGame:
...
ld a, TRUE
ld [wSaveFileExists], a
farcall StageRTCTimeForSave
farcall BackupMysteryGift
- call ValidateSave
+ call InvalidateSave
call SaveOptions
call SavePlayerData
call SavePokemonData
call SaveChecksum
- call ValidateBackupSave
+ call ValidateSave
+ call InvalidateBackupSave
call SaveBackupOptions
call SaveBackupPlayerData
call SaveBackupPokemonData
call SaveBackupChecksum
+ call ValidateBackupSave
farcall BackupPartyMonMail
farcall BackupMobileEventIndex
farcall SaveRTC
...
```
```diff
_SaveGameData:
...
ld a, TRUE
ld [wSaveFileExists], a
farcall StageRTCTimeForSave
farcall BackupMysteryGift
- call ValidateSave
+ call InvalidateSave
call SaveOptions
call SavePlayerData
call SavePokemonData
call SaveBox
call SaveChecksum
- call ValidateBackupSave
+ call ValidateSave
+ call InvalidateBackupSave
call SaveBackupOptions
call SaveBackupPlayerData
call SaveBackupPokemonData
call SaveBackupChecksum
+ call ValidateBackupSave
call UpdateStackTop
farcall BackupPartyMonMail
farcall BackupMobileEventIndex
farcall SaveRTC
...
```
Then create two new routines, `InvalidateSave` and `InvalidateBackupSave`:
```diff
ValidateSave:
ld a, BANK(sCheckValue1) ; aka BANK(sCheckValue2)
call GetSRAMBank
ld a, SAVE_CHECK_VALUE_1
ld [sCheckValue1], a
ld a, SAVE_CHECK_VALUE_2
ld [sCheckValue2], a
jp CloseSRAM
+InvalidateSave:
+ ld a, BANK(sCheckValue1) ; aka BANK(sCheckValue2)
+ call GetSRAMBank
+ xor a
+ ld [sCheckValue1], a
+ ld [sCheckValue2], a
+ jp CloseSRAM
```
```diff
ValidateBackupSave:
ld a, BANK(sBackupCheckValue1) ; aka BANK(sBackupCheckValue2)
call GetSRAMBank
ld a, SAVE_CHECK_VALUE_1
ld [sBackupCheckValue1], a
ld a, SAVE_CHECK_VALUE_2
ld [sBackupCheckValue2], a
jp CloseSRAM
+InvalidateBackupSave:
+ ld a, BANK(sBackupCheckValue1) ; aka BANK(sBackupCheckValue2)
+ call GetSRAMBank
+ xor a
+ ld [sBackupCheckValue1], a
+ ld [sBackupCheckValue2], a
+ jp CloseSRAM
```
## Moves that lower Defense can do so after breaking a Substitute
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=OGwKPRJLaaI))
This bug affects Acid, Iron Tail, and Rock Smash.
**Fix:** Edit `DefenseDownHit` in [data/moves/effects.asm](https://github.com/pret/pokecrystal/blob/master/data/moves/effects.asm):
```diff
DefenseDownHit:
checkobedience
usedmovetext
doturn
critical
damagestats
damagecalc
stab
damagevariation
checkhit
effectchance
hittarget
failuretext
checkfaint
criticaltext
supereffectivetext
checkfaint
buildopponentrage
- effectchance ; bug: duplicate effectchance shouldn't be here
defensedown
statdownmessage
endmove
```
## Counter and Mirror Coat still work if the opponent uses an item
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=uRYyzKRatFk))
**Fix:** Edit `BattleCommand_Counter` in [engine/battle/move_effects/counter.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/move_effects/counter.asm) and `BattleCommand_MirrorCoat` in [engine/battle/move_effects/mirror_coat.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/move_effects/mirror_coat.asm):
```diff
- ; BUG: Move should fail with all non-damaging battle actions
ld hl, wCurDamage
ld a, [hli]
or [hl]
- ret z
+ jr z, .failed
```
Add this to the end of each file:
```diff
+.failed
+ ld a, 1
+ ld [wEffectFailed], a
+ and a
+ ret
```
## A Disabled but PP Up–enhanced move may not trigger Struggle
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=1v9x4SgMggs))
**Fix:** Edit `CheckPlayerHasUsableMoves` in [engine/battle/core.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/core.asm):
```diff
.done
- ; Bug: this will result in a move with PP Up confusing the game.
- and a ; should be "and PP_MASK"
+ and PP_MASK
ret nz
.force_struggle
ld hl, BattleText_MonHasNoMovesLeft
call StdBattleTextbox
ld c, 60
call DelayFrames
xor a
ret
```
## A Pokémon that fainted from Pursuit will have its old status condition when revived
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=tiRvw-Nb2ME))
**Fix:** Edit `PursuitSwitch` in [engine/battle/core.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/core.asm)
```diff
ld a, $f0
ld [wCryTracks], a
ld a, [wBattleMonSpecies]
call PlayStereoCry
+ ld a, [wCurBattleMon]
+ push af
ld a, [wLastPlayerMon]
+ ld [wCurBattleMon], a
+ call UpdateFaintedPlayerMon
+ pop af
+ ld [wCurBattleMon], a
- ld c, a
- ld hl, wBattleParticipantsNotFainted
- ld b, RESET_FLAG
- predef SmallFarFlagAction
call PlayerMonFaintedAnimation
ld hl, BattleText_MonFainted
jr .done_fainted
```
## Lock-On and Mind Reader don't always bypass Fly and Dig
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
This bug affects Attract, Curse, Foresight, Mean Look, Mimic, Nightmare, Spider Web, Transform, and stat-lowering effects of moves like String Shot or Bubble during the semi-invulnerable turn of Fly or Dig.
**Fix:** Edit `CheckHiddenOpponent` in [engine/battle/effect_commands.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/effect_commands.asm):
```diff
CheckHiddenOpponent:
-; BUG: This routine is completely redundant and introduces a bug, since BattleCommand_CheckHit does these checks properly.
- ld a, BATTLE_VARS_SUBSTATUS3_OPP
- call GetBattleVar
- and 1 << SUBSTATUS_FLYING | 1 << SUBSTATUS_UNDERGROUND
+ xor a
ret
```
## Wild Pokémon can always Teleport regardless of level difference
**Fix:** Edit `BattleCommand_Teleport` in [engine/battle/move_effects/teleport.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/move_effects/teleport.asm):
```diff
.loop_enemy
call BattleRandom
cp c
jr nc, .loop_enemy
srl b
srl b
cp b
- ; This should be jr c, .failed
- ; As written, it makes enemy use of Teleport always succeed if able
- jr nc, .run_away
+ jr c, .failed
```
## Beat Up can desynchronize link battles
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=202-iAsrIa8))
**Fix:** Edit `BattleCommand_BeatUp` in [engine/battle/move_effects/beat_up.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/move_effects/beat_up.asm):
```diff
.got_mon
ld a, [wd002]
ld hl, wPartyMonNicknames
call GetNick
ld a, MON_HP
call GetBeatupMonLocation
ld a, [hli]
or [hl]
jp z, .beatup_fail ; fainted
ld a, [wd002]
ld c, a
ld a, [wCurBattleMon]
- ; BUG: this can desynchronize link battles
- ; Change "cp [hl]" to "cp c" to fix
- cp [hl]
+ cp c
ld hl, wBattleMonStatus
jr z, .active_mon
ld a, MON_STATUS
call GetBeatupMonLocation
.active_mon
ld a, [hl]
and a
jp nz, .beatup_fail
```
## Beat Up works incorrectly with only one Pokémon in the party
*Fixing this bug may break compatibility with standard Pokémon Crystal for link battles.*
This bug prevents the rest of Beat Up's effect from being executed if the player or enemy only has one Pokémon in their party while using it. It prevents Substitute from being raised and King's Rock from working.
**Fix:** Edit `BattleCommand_EndLoop` in [engine/battle/effect_commands.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/effect_commands.asm):
```diff
.only_one_beatup
ld a, BATTLE_VARS_SUBSTATUS3
call GetBattleVarAddr
res SUBSTATUS_IN_LOOP, [hl]
- call BattleCommand_BeatUpFailText
- jp EndMoveEffect
+ ret
```
**Cosmetic fix:** This fix does not break compatibility, but it only affects what's shown on the screen for the patched game.
```diff
.only_one_beatup
ld a, BATTLE_VARS_SUBSTATUS3
call GetBattleVarAddr
res SUBSTATUS_IN_LOOP, [hl]
call BattleCommand_BeatUpFailText
+ call BattleCommand_RaiseSub
jp EndMoveEffect
```
## Beat Up may fail to raise Substitute
This bug prevents Substitute from being raised if Beat Up was blocked by Protect or Detect.
**Fix:** Edit `BattleCommand_FailureText` in [engine/battle/effect_commands.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/effect_commands.asm).
```diff
cp EFFECT_MULTI_HIT
jr z, .multihit
cp EFFECT_DOUBLE_HIT
jr z, .multihit
cp EFFECT_POISON_MULTI_HIT
jr z, .multihit
+ cp EFFECT_BEAT_UP
+ jr z, .multihit
jp EndMoveEffect
.multihit
call BattleCommand_RaiseSub
jp EndMoveEffect
```
## Beat Up may trigger King's Rock even if it failed
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
This bug is caused because Beat Up never sets `wAttackMissed`, even when no Pokémon was able to attack (due to being fainted or having a status condition).
**Fix:** Edit `BattleCommand_BeatUpFailText` in [engine/battle/move_effects/beat_up.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/move_effects/beat_up.asm):
```diff
BattleCommand_BeatUpFailText:
; beatupfailtext
ld a, [wBeatUpHitAtLeastOnce]
and a
ret nz
+
+ inc a
+ ld [wAttackMissed], a
jp PrintButItFailed
```
## Present damage is incorrect in link battles
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
([Video](https://www.youtube.com/watch?v=XJaQoKtrEuw))
This bug existed for all battles in Gold and Silver, and was only fixed for single-player battles in Crystal to preserve link compatibility.
**Fix:** Edit `BattleCommand_Present` in [engine/battle/move_effects/present.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/move_effects/present.asm):
```diff
BattleCommand_Present:
; present
- ld a, [wLinkMode]
- cp LINK_COLOSSEUM
- jr z, .colosseum_skippush
push bc
push de
-.colosseum_skippush
-
call BattleCommand_Stab
-
- ld a, [wLinkMode]
- cp LINK_COLOSSEUM
- jr z, .colosseum_skippop
pop de
pop bc
-.colosseum_skippop
```
## A Transformed Pokémon can use Sketch and learn otherwise unobtainable moves
([Video](https://www.youtube.com/watch?v=AFiBxAOkCGI))
**Fix:** Edit `BattleCommand_Sketch` in [engine/battle/move_effects/sketch.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/move_effects/sketch.asm):
```diff
-; If the opponent is transformed, fail.
+; If the user is transformed, fail.
- ld a, BATTLE_VARS_SUBSTATUS5_OPP
+ ld a, BATTLE_VARS_SUBSTATUS5
call GetBattleVarAddr
bit SUBSTATUS_TRANSFORMED, [hl]
jp nz, .fail
```
## "Smart" AI encourages Mean Look if its own Pokémon is badly poisoned
([Video](https://www.youtube.com/watch?v=cygMO-zHTls))
**Fix:** Edit `AI_Smart_MeanLook` in [engine/battle/ai/scoring.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/ai/scoring.asm):
```diff
-; 80% chance to greatly encourage this move if the enemy is badly poisoned (buggy).
-; Should check wPlayerSubStatus5 instead.
- ld a, [wEnemySubStatus5]
+; 80% chance to greatly encourage this move if the player is badly poisoned
+ ld a, [wPlayerSubStatus5]
bit SUBSTATUS_TOXIC, a
jr nz, .asm_38e26
```
## AI makes a false assumption about `CheckTypeMatchup`
**Fix:** Edit `BattleCheckTypeMatchup` in [engine/battle/effect_commands.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/effect_commands.asm):
```diff
BattleCheckTypeMatchup:
ld hl, wEnemyMonType1
ldh a, [hBattleTurn]
and a
- jr z, CheckTypeMatchup
+ jr z, .get_type
ld hl, wBattleMonType1
+.get_type
+ ld a, BATTLE_VARS_MOVE_TYPE
+ call GetBattleVar ; preserves hl, de, and bc
CheckTypeMatchup:
-; There is an incorrect assumption about this function made in the AI related code: when
-; the AI calls CheckTypeMatchup (not BattleCheckTypeMatchup), it assumes that placing the
-; offensive type in a will make this function do the right thing. Since a is overwritten,
-; this assumption is incorrect. A simple fix would be to load the move type for the
-; current move into a in BattleCheckTypeMatchup, before falling through, which is
-; consistent with how the rest of the code assumes this code works like.
push hl
push de
push bc
- ld a, BATTLE_VARS_MOVE_TYPE
- call GetBattleVar
ld d, a
...
```
## NPC use of Full Heal or Full Restore does not cure Nightmare status
([Video](https://www.youtube.com/watch?v=rGqu3d3pdok&t=322))
**Fix:** Edit `AI_HealStatus` in [engine/battle/ai/items.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/ai/items.asm):
```diff
AI_HealStatus:
ld a, [wCurOTMon]
ld hl, wOTPartyMon1Status
ld bc, PARTYMON_STRUCT_LENGTH
call AddNTimes
xor a
ld [hl], a
ld [wEnemyMonStatus], a
- ; Bug: this should reset SUBSTATUS_NIGHTMARE
- ; Uncomment the 2 lines below to fix
- ; ld hl, wEnemySubStatus1
- ; res SUBSTATUS_NIGHTMARE, [hl]
+ ld hl, wEnemySubStatus1
+ res SUBSTATUS_NIGHTMARE, [hl]
; Bug: this should reset SUBSTATUS_CONFUSED
; Uncomment the 2 lines below to fix
; ld hl, wEnemySubStatus3
; res SUBSTATUS_CONFUSED, [hl]
ld hl, wEnemySubStatus5
res SUBSTATUS_TOXIC, [hl]
ret
```
## NPC use of Full Heal does not cure confusion status
**Fix:** Edit `EnemyUsedFullRestore`, `EnemyUsedFullHeal`, and `AI_HealStatus` in [engine/battle/ai/items.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/ai/items.asm):
```diff
EnemyUsedFullRestore:
call AI_HealStatus
ld a, FULL_RESTORE
ld [wCurEnemyItem], a
- ld hl, wEnemySubStatus3
- res SUBSTATUS_CONFUSED, [hl]
xor a
ld [wEnemyConfuseCount], a
```
```diff
EnemyUsedFullHeal:
call AIUsedItemSound
call AI_HealStatus
ld a, FULL_HEAL
+ ld [wCurEnemyItem], a
+ xor a
+ ld [wEnemyConfuseCount], a
jp PrintText_UsedItemOn_AND_AIUpdateHUD
```
```diff
AI_HealStatus:
ld a, [wCurOTMon]
ld hl, wOTPartyMon1Status
ld bc, PARTYMON_STRUCT_LENGTH
call AddNTimes
xor a
ld [hl], a
ld [wEnemyMonStatus], a
; Bug: this should reset SUBSTATUS_NIGHTMARE
; Uncomment the 2 lines below to fix
; ld hl, wEnemySubStatus1
; res SUBSTATUS_NIGHTMARE, [hl]
- ; Bug: this should reset SUBSTATUS_CONFUSED
- ; Uncomment the 2 lines below to fix
- ; ld hl, wEnemySubStatus3
- ; res SUBSTATUS_CONFUSED, [hl]
+ ld hl, wEnemySubStatus3
+ res SUBSTATUS_CONFUSED, [hl]
ld hl, wEnemySubStatus5
res SUBSTATUS_TOXIC, [hl]
ret
```
## HP bar animation is slow for high HP
([Video](https://www.youtube.com/watch?v=SE-BfsFgZVM))
**Fix:** Edit `LongAnim_UpdateVariables` in [engine/battle/anim_hp_bar.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/anim_hp_bar.asm):
```diff
- ; This routine is buggy. The result from ComputeHPBarPixels is stored
- ; in e. However, the pop de opcode deletes this result before it is even
- ; used. The game then proceeds as though it never deleted that output.
- ; To fix, uncomment the line below.
call ComputeHPBarPixels
- ; ld a, e
+ ld a, e
pop bc
pop de
pop hl
- ld a, e ; Comment or delete this line to fix the above bug.
ld hl, wCurHPBarPixels
cp [hl]
jr z, .loop
ld [hl], a
and a
ret
```
## HP bar animation off-by-one error for low HP
([Video](https://www.youtube.com/watch?v=9KyNVIZxJvI))
**Fix:** Edit `ShortHPBar_CalcPixelFrame` in [engine/battle/anim_hp_bar.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/anim_hp_bar.asm):
```diff
ld b, 0
-; This routine is buggy. If [wCurHPAnimMaxHP] * [wCurHPBarPixels] is
-; divisible by HP_BAR_LENGTH_PX, the loop runs one extra time.
-; To fix, uncomment the line below.
.loop
ld a, l
sub HP_BAR_LENGTH_PX
ld l, a
ld a, h
sbc $0
ld h, a
- ; jr z, .done
+ jr z, .done
jr c, .done
inc b
jr .loop
```
## Experience underflow for level 1 Pokémon with Medium-Slow growth rate
([Video](https://www.youtube.com/watch?v=SXH8u0plHrE))
This can bring Pokémon straight from level 1 to 100 by gaining just a few experience points.
**Fix:** Edit `CalcExpAtLevel` in [engine/pokemon/experience.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokemon/experience.asm):
```diff
CalcExpAtLevel:
; (a/b)*n**3 + c*n**2 + d*n - e
+ ld a, d
+ cp 1
+ jr nz, .UseExpFormula
+; Pokémon have 0 experience at level 1
+ xor a
+ ld hl, hProduct
+ ld [hli], a
+ ld [hli], a
+ ld [hli], a
+ ld [hl], a
+ ret
+
+.UseExpFormula
ld a, [wBaseGrowthRate]
add a
add a
ld c, a
ld b, 0
ld hl, GrowthRates
add hl, bc
```
## Five-digit experience gain is printed incorrectly
([Video](https://www.youtube.com/watch?v=o54VjpAEoO8))
**Fix:** Edit `_BoostedExpPointsText` and `_ExpPointsText` in [data/text/common_2.asm](https://github.com/pret/pokecrystal/blob/master/data/text/common_2.asm):
```diff
_BoostedExpPointsText::
text_start
line "a boosted"
cont "@"
- text_decimal wStringBuffer2, 2, 4
+ text_decimal wStringBuffer2, 2, 5
text " EXP. Points!"
prompt
_ExpPointsText::
text_start
line "@"
- text_decimal wStringBuffer2, 2, 4
+ text_decimal wStringBuffer2, 2, 5
text " EXP. Points!"
prompt
```
## BRN/PSN/PAR do not affect catch rate
**Fix:** Edit `PokeBallEffect` in [engine/items/item_effects.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/item_effects.asm):
```diff
-; This routine is buggy. It was intended that SLP and FRZ provide a higher
-; catch rate than BRN/PSN/PAR, which in turn provide a higher catch rate than
-; no status effect at all. But instead, it makes BRN/PSN/PAR provide no
-; benefit.
-; Uncomment the line below to fix this.
ld b, a
ld a, [wEnemyMonStatus]
and 1 << FRZ | SLP
ld c, 10
jr nz, .addstatus
- ; ld a, [wEnemyMonStatus]
+ ld a, [wEnemyMonStatus]
and a
ld c, 5
jr nz, .addstatus
ld c, 0
.addstatus
ld a, b
add c
jr nc, .max_1
ld a, $ff
.max_1
```
## Moon Ball does not boost catch rate
**Fix:** Edit `MoonBallMultiplier` in [items/item_effects.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/item_effects.asm):
```diff
-; Moon Stone's constant from Pokémon Red is used.
-; No Pokémon evolve with Burn Heal,
-; so Moon Balls always have a catch rate of 1×.
push bc
ld a, BANK("Evolutions and Attacks")
call GetFarByte
- cp MOON_STONE_RED ; BURN_HEAL
+ cp MOON_STONE
pop bc
ret nz
```
## Love Ball boosts catch rate for the wrong gender
**Fix:** Edit `LoveBallMultiplier` in [items/item_effects.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/item_effects.asm):
```diff
.wildmale
ld a, d
pop de
cp d
pop bc
- ret nz ; for the intended effect, this should be "ret z"
+ ret z
```
## Fast Ball only boosts catch rate for three Pokémon
**Fix:** Edit `FastBallMultiplier` in [items/item_effects.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/item_effects.asm):
```diff
.loop
ld a, BANK(FleeMons)
call GetFarByte
inc hl
cp -1
jr z, .next
cp c
- jr nz, .next ; for the intended effect, this should be "jr nz, .loop"
+ jr nz, .loop
sla b
jr c, .max
```
## Dragon Scale, not Dragon Fang, boosts Dragon-type moves
*Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.*
**Fix:** Edit `ItemAttributes` in [data/items/attributes.asm](https://github.com/pret/pokecrystal/blob/master/data/items/attributes.asm):
```diff
; DRAGON_FANG
- item_attribute 100, HELD_NONE, 0, CANT_SELECT, ITEM, ITEMMENU_NOUSE, ITEMMENU_NOUSE
+ item_attribute 100, HELD_DRAGON_BOOST, 10, CANT_SELECT, ITEM, ITEMMENU_NOUSE, ITEMMENU_NOUSE
...
; DRAGON_SCALE
- item_attribute 2100, HELD_DRAGON_BOOST, 10, CANT_SELECT, ITEM, ITEMMENU_NOUSE, ITEMMENU_NOUSE
+ item_attribute 2100, HELD_NONE, 0, CANT_SELECT, ITEM, ITEMMENU_NOUSE, ITEMMENU_NOUSE
```
## Clair can give TM24 Dragonbreath twice
([Video](https://www.youtube.com/watch?v=8BvBjqxmyOk))
**Fix:** Edit `DragonsDen1F_MapScripts` in [maps/DragonsDen1F.asm](https://github.com/pret/pokecrystal/blob/master/maps/DragonsDen1F.asm):
```diff
- db 0 ; callbacks
+ db 1 ; callbacks
+ callback MAPCALLBACK_NEWMAP, .UnsetClairScene
+
+.UnsetClairScene:
+ setmapscene DRAGONS_DEN_B1F, SCENE_DRAGONSDENB1F_NOTHING
+ return
```
## Daisy's grooming doesn't always increase happiness
This is a bug with `HaircutOrGrooming` in [engine/events/haircut.asm](https://github.com/pret/pokecrystal/blob/master/engine/events/haircut.asm):
```asm
; Bug: Subtracting $ff from $ff fails to set c.
; This can result in overflow into the next data array.
; In the case of getting a grooming from Daisy, we bleed
; into CopyPokemonName_Buffer1_Buffer3, which passes
; $d0 to ChangeHappiness and returns $73 to the script.
; The end result is that there is a 0.4% chance your
; Pokemon's happiness will not change at all.
.loop
sub [hl]
jr c, .ok
inc hl
inc hl
inc hl
jr .loop
.ok
inc hl
ld a, [hli]
ld [wScriptVar], a
ld c, [hl]
call ChangeHappiness
ret
...
INCLUDE "data/events/happiness_probabilities.asm"
CopyPokemonName_Buffer1_Buffer3:
ld hl, wStringBuffer1
ld de, wStringBuffer3
ld bc, MON_NAME_LENGTH
jp CopyBytes
```
**Fix:** Edit [data/events/happiness_probabilities.asm](https://github.com/pret/pokecrystal/blob/master/data/events/happiness_probabilities.asm):
```diff
HappinessData_DaisysGrooming:
- db $ff, 2, HAPPINESS_GROOMING ; 99.6% chance
+ db $80, 2, HAPPINESS_GROOMING ; 50% chance
+ db $ff, 2, HAPPINESS_GROOMING ; 50% chance
```
## Magikarp in Lake of Rage are shorter, not longer
**Fix:** Edit `LoadEnemyMon.CheckMagikarpArea` in [engine/battle/core.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/core.asm):
```diff
.CheckMagikarpArea:
-; The "jr z" checks are supposed to be "jr nz".
-
-; Instead, all maps in GROUP_LAKE_OF_RAGE (Mahogany area)
-; and Routes 20 and 44 are treated as Lake of Rage.
-
-; This also means Lake of Rage Magikarp can be smaller than ones
-; caught elsewhere rather than the other way around.
-
-; Intended behavior enforces a minimum size at Lake of Rage.
-; The real behavior prevents a minimum size in the Lake of Rage area.
-
-; Moreover, due to the check not being translated to feet+inches, all Magikarp
-; smaller than 4'0" may be caught by the filter, a lot more than intended.
ld a, [wMapGroup]
cp GROUP_LAKE_OF_RAGE
- jr z, .Happiness
+ jr nz, .Happiness
ld a, [wMapNumber]
cp MAP_LAKE_OF_RAGE
- jr z, .Happiness
+ jr nz, .Happiness
```
## Magikarp length limits have a unit conversion error
**Fix:** Edit `LoadEnemyMon.CheckMagikarpArea` in [engine/battle/core.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/core.asm):
```diff
; Get Magikarp's length
ld de, wEnemyMonDVs
ld bc, wPlayerID
callfar CalcMagikarpLength
; No reason to keep going if length > 1536 mm (i.e. if HIGH(length) > 6 feet)
ld a, [wMagikarpLength]
- cp HIGH(1536) ; should be "cp 5", since 1536 mm = 5'0", but HIGH(1536) = 6
+ cp 5
jr nz, .CheckMagikarpArea
; 5% chance of skipping both size checks
call Random
cp 5 percent
jr c, .CheckMagikarpArea
; Try again if length >= 1616 mm (i.e. if LOW(length) >= 4 inches)
ld a, [wMagikarpLength + 1]
- cp LOW(1616) ; should be "cp 4", since 1616 mm = 5'4", but LOW(1616) = 80
+ cp 4
jr nc, .GenerateDVs
; 20% chance of skipping this check
call Random
cp 20 percent - 1
jr c, .CheckMagikarpArea
; Try again if length >= 1600 mm (i.e. if LOW(length) >= 3 inches)
ld a, [wMagikarpLength + 1]
- cp LOW(1600) ; should be "cp 3", since 1600 mm = 5'3", but LOW(1600) = 64
+ cp 3
jr nc, .GenerateDVs
```
**Better fix:** Rewrite the whole system to use millimeters instead of feet and inches, since they have better precision (1 in = 25.4 mm); and only convert from metric to imperial units for display purposes (or don't, of course).
## Magikarp lengths can be miscalculated
**Fix:** Edit `CalcMagikarpLength.BCLessThanDE` in [engine/events/magikarp.asm](https://github.com/pret/pokecrystal/blob/master/engine/events/magikarp.asm):
```diff
.BCLessThanDE:
-; Intention: Return bc < de.
-; Reality: Return b < d.
ld a, b
cp d
ret c
- ret nc ; whoops
ld a, c
cp e
ret
```
## Battle transitions fail to account for the enemy's level
([Video](https://www.youtube.com/watch?v=eij_1060SMc))
There are three things wrong here:
- `wEnemyMonLevel` isn't initialized yet
- `wBattleMonLevel` gets overwritten after it's initialized by `FindFirstAliveMonAndStartBattle`
- `wBattleMonLevel` isn't initialized until much later when the battle is with a trainer
**Fix:**
First, edit [engine/battle/battle_transition.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/battle_transition.asm):
```diff
StartTrainerBattle_DetermineWhichAnimation:
; The screen flashes a different number of times depending on the level of
; your lead Pokemon relative to the opponent's.
-; BUG: wBattleMonLevel and wEnemyMonLevel are not set at this point, so whatever
-; values happen to be there will determine the animation.
+ ld a, [wOtherTrainerClass]
+ and a
+ jr z, .wild
+ farcall SetTrainerBattleLevel
+
+.wild
+ ld b, PARTY_LENGTH
+ ld hl, wPartyMon1HP
+ ld de, PARTYMON_STRUCT_LENGTH - 1
+
+.loop
+ ld a, [hli]
+ or [hl]
+ jr nz, .okay
+ add hl, de
+ dec b
+ jr nz, .loop
+
+.okay
+ ld de, MON_LEVEL - MON_HP - 1
+ add hl, de
ld de, 0
- ld a, [wBattleMonLevel]
+ ld a, [hl]
add 3
- ld hl, wEnemyMonLevel
+ ld hl, wCurPartyLevel
cp [hl]
jr nc, .not_stronger
set TRANS_STRONGER_F, e
.not_stronger
ld a, [wEnvironment]
cp CAVE
jr z, .cave
cp ENVIRONMENT_5
jr z, .cave
cp DUNGEON
jr z, .cave
set TRANS_NO_CAVE_F, e
.cave
ld hl, .StartingPoints
add hl, de
ld a, [hl]
ld [wJumptableIndex], a
ret
.StartingPoints:
; entries correspond to TRANS_* constants
db BATTLETRANSITION_CAVE
db BATTLETRANSITION_CAVE_STRONGER
db BATTLETRANSITION_NO_CAVE
db BATTLETRANSITION_NO_CAVE_STRONGER
```
Then edit [engine/battle/start_battle.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/start_battle.asm):
```diff
FindFirstAliveMonAndStartBattle:
xor a
ldh [hMapAnims], a
call DelayFrame
- ld b, PARTY_LENGTH
- ld hl, wPartyMon1HP
- ld de, PARTYMON_STRUCT_LENGTH - 1
-
-.loop
- ld a, [hli]
- or [hl]
- jr nz, .okay
- add hl, de
- dec b
- jr nz, .loop
-
-.okay
- ld de, MON_LEVEL - MON_HP
- add hl, de
- ld a, [hl]
- ld [wBattleMonLevel], a
predef DoBattleTransition
```
Finally, edit [engine/battle/read_trainer_party.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/read_trainer_party.asm):
```diff
INCLUDE "data/trainers/parties.asm"
+
+SetTrainerBattleLevel:
+ ld a, 255
+ ld [wCurPartyLevel], a
+
+ ld a, [wInBattleTowerBattle]
+ bit 0, a
+ ret nz
+
+ ld a, [wLinkMode]
+ and a
+ ret nz
+
+ ld a, [wOtherTrainerClass]
+ dec a
+ ld c, a
+ ld b, 0
+ ld hl, TrainerGroups
+ add hl, bc
+ add hl, bc
+ ld a, [hli]
+ ld h, [hl]
+ ld l, a
+
+ ld a, [wOtherTrainerID]
+ ld b, a
+.skip_trainer
+ dec b
+ jr z, .got_trainer
+.skip_party
+ ld a, [hli]
+ cp $ff
+ jr nz, .skip_party
+ jr .skip_trainer
+.got_trainer
+
+.skip_name
+ ld a, [hli]
+ cp "@"
+ jr nz, .skip_name
+
+ inc hl
+ ld a, [hl]
+ ld [wCurPartyLevel], a
+ ret
```
## A "HOF Master!" title for 200-Time Famers is defined but inaccessible
([Video](https://www.youtube.com/watch?v=iHkWubvxmSg))
**Fix:** Edit `_HallOfFamePC.DisplayMonAndStrings` in [engine/events/halloffame.asm](https://github.com/pret/pokecrystal/blob/master/engine/events/halloffame.asm):
```diff
ld a, [wHallOfFameTempWinCount]
- cp HOF_MASTER_COUNT + 1 ; should be HOF_MASTER_COUNT
+ cp HOF_MASTER_COUNT
jr c, .print_num_hof
ld de, .HOFMaster
hlcoord 1, 2
call PlaceString
hlcoord 13, 2
jr .finish
```
## Slot machine payout sound effects cut each other off
([Video](https://www.youtube.com/watch?v=ojq3xqfRF6I))
**Fix:** Edit `SlotsAction_PayoutAnim` in [engine/games/slot_machine.asm](https://github.com/pret/pokecrystal/blob/master/engine/games/slot_machine.asm):
```diff
.okay
ld [hl], e
dec hl
ld [hl], d
ld a, [wSlotsDelay]
and $7
- ret z ; ret nz would be more appropriate
+ ret nz
ld de, SFX_GET_COIN_FROM_SLOTS
call PlaySFX
ret
```
## Team Rocket battle music is not used for Executives or Scientists
**Fix:** Edit `PlayBattleMusic` in [engine/battle/start_battle.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/start_battle.asm):
```diff
ld de, MUSIC_ROCKET_BATTLE
cp GRUNTM
jr z, .done
cp GRUNTF
jr z, .done
+ cp EXECUTIVEM
+ jr z, .done
+ cp EXECUTIVEF
+ jr z, .done
+ cp SCIENTIST
+ jr z, .done
```
## No bump noise if standing on tile `$3E`
**Fix:** Edit `DoPlayerMovement.CheckWarp` in [engine/overworld/player_movement.asm](https://github.com/pret/pokecrystal/blob/master/engine/overworld/player_movement.asm):
```diff
.CheckWarp:
-; Bug: Since no case is made for STANDING here, it will check
-; [.edgewarps + $ff]. This resolves to $3e at $8035a.
-; This causes wWalkingIntoEdgeWarp to be nonzero when standing on tile $3e,
-; making bumps silent.
-
ld a, [wWalkingDirection]
- ; cp STANDING
- ; jr z, .not_warp
+ cp STANDING
+ jr z, .not_warp
ld e, a
ld d, 0
ld hl, .EdgeWarps
add hl, de
ld a, [wPlayerStandingTile]
cp [hl]
jr nz, .not_warp
ld a, TRUE
ld [wWalkingIntoEdgeWarp], a
ld a, [wWalkingDirection]
- ; This is in the wrong place.
- cp STANDING
- jr z, .not_warp
```
## Playing Entei's Pokédex cry can distort Raikou's and Suicune's
([Video](https://www.youtube.com/watch?v=z305e4sIO24))
The exact cause of this bug is unknown.
**Workaround:** Edit `DexEntryScreen_MenuActionJumptable.Cry` in [engine/pokedex/pokedex.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokedex/pokedex.asm):
```diff
.Cry:
- call Pokedex_GetSelectedMon
- ld a, [wTempSpecies]
- call GetCryIndex
- ld e, c
- ld d, b
- call PlayCry
+ ld a, [wCurPartySpecies]
+ call PlayMonCry
ret
```
## In-battle “`…`” ellipsis is too high
This is a mistake with the “`…`” tile in [gfx/battle/hp_exp_bar_border.png](https://github.com/pret/pokecrystal/blob/master/gfx/battle/hp_exp_bar_border.png):
**Fix:** Lower the ellipsis by two pixels:
## Move selection menu doesn't handle joypad properly
([Video](https://www.youtube.com/watch?v=vjFUo6Jr4po&t=438))
`hInMenu` isn't defined in the menu that handles selecting moves in a battle. Because of this, your cursor is usually rendered unable to keep scrolling when one of the directional keys is being held. It's up for debate whether this behavior was intentional or not, but this value should be defined when in the move selection menu. A value of 1 will allow it to keep scrolling, though it's usually 0 by default.
There exists one way in which this behaviour would be temporarily changed in-game, and that's when the credits sequence is triggered, `hInMenu` will be set but never unset. This can be fixed with the following:
**Fix:** Edit `Credits` in [engine/movie/credits.asm](https://github.com/pret/pokecrystal/blob/master/engine/movie/credits.asm):
```diff
ldh a, [hVBlank]
push af
ld a, $5
ldh [hVBlank], a
+ ldh a, [hInMenu]
+ push af
ld a, $1
ldh [hInMenu], a
...
ldh [hLCDCPointer], a
ldh [hBGMapAddress], a
+ pop af
+ ldh [hInMenu], a
pop af
ldh [hVBlank], a
pop af
ldh [rSVBK], a
```
If you want to make sure `hInMenu` always has a defined value in the move selection menu, the following code will set it to 1:
**Fix:** Edit `BattleTurn` in [engine/battle/core.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/core.asm):
```diff
BattleTurn:
+ ldh a, [hInMenu]
+ push af
+ ld a, 1
+ ldh [hInMenu], a
+
.loop
...
jp .loop
.quit
+ pop af
+ ldh [hInMenu], a
ret
```
## Two tiles in the `port` tileset are drawn incorrectly
This is a mistake with the left-hand warp carpet corner tiles in [gfx/tilesets/port.png](https://github.com/pret/pokecrystal/blob/master/gfx/tilesets/port.png):
**Fix:** Adjust them to match the right-hand corner tiles:
## `LoadMetatiles` wraps around past 128 blocks
This bug prevents you from using blocksets with more than 128 blocks.
**Fix:** Edit `LoadMetatiles` in [home/map.asm](https://github.com/pret/pokecrystal/blob/master/home/map.asm):
```diff
; Set hl to the address of the current metatile data ([wTilesetBlocksAddress] + (a) tiles).
- ; This is buggy; it wraps around past 128 blocks.
- ; To fix, uncomment the line below.
- add a ; Comment or delete this line to fix the above bug.
ld l, a
ld h, 0
- ; add hl, hl
+ add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld a, [wTilesetBlocksAddress]
add l
ld l, a
ld a, [wTilesetBlocksAddress + 1]
adc h
ld h, a
```
## Surfing directly across a map connection does not load the new map
([Video](https://www.youtube.com/watch?v=XFOWvMNG-zw))
**Fix:**
First, edit `UsedSurfScript` in [engine/events/overworld.asm](https://github.com/pret/pokecrystal/blob/master/engine/events/overworld.asm):
```diff
UsedSurfScript:
writetext UsedSurfText ; "used SURF!"
waitbutton
closetext
callasm .empty_fn ; empty function
readmem wBuffer2
writevar VAR_MOVEMENT
special ReplaceKrisSprite
special PlayMapMusic
-; step into the water (slow_step DIR, step_end)
special SurfStartStep
- applymovement PLAYER, wMovementBuffer
end
```
Then edit `SurfStartStep` in [engine/overworld/player_object.asm](https://github.com/pret/pokecrystal/blob/master/engine/overworld/player_object.asm):
```diff
SurfStartStep:
- call InitMovementBuffer
- call .GetMovementData
- call AppendToMovementBuffer
- ld a, movement_step_end
- call AppendToMovementBuffer
- ret
-
-.GetMovementData:
ld a, [wPlayerDirection]
srl a
srl a
maskbits NUM_DIRECTIONS
ld e, a
ld d, 0
ld hl, .movement_data
add hl, de
- ld a, [hl]
- ret
+ add hl, de
+ add hl, de
+ ld a, BANK(.movement_data)
+ jp StartAutoInput
.movement_data
- slow_step DOWN
- slow_step UP
- slow_step LEFT
- slow_step RIGHT
+ db D_DOWN, 0, -1
+ db D_UP, 0, -1
+ db D_LEFT, 0, -1
+ db D_RIGHT, 0, -1
```
## Swimming NPCs aren't limited by their movement radius
This bug is why the Lapras in [maps/UnionCaveB2F.asm](https://github.com/pret/pokecrystal/blob/master/maps/UnionCaveB2F.asm), which uses `SPRITEMOVEDATA_SWIM_WANDER`, is not restricted by its `1, 1` movement radius.
**Fix:** Edit `CanObjectMoveInDirection` in [engine/overworld/npc_movement.asm](https://github.com/pret/pokecrystal/blob/master/engine/overworld/npc_movement.asm):
```diff
ld hl, OBJECT_FLAGS1
add hl, bc
bit NOCLIP_TILES_F, [hl] ; lost, uncomment next line to fix
- ; jr nz, .noclip_tiles
+ jr nz, .noclip_tiles
```
## `CheckOwnMon` only checks the first five letters of OT names
([Video](https://www.youtube.com/watch?v=GVTTmReM4nQ))
This bug can allow you to talk to Eusine in Celadon City and encounter Ho-Oh with only traded legendary beasts.
**Fix:** Edit `CheckOwnMon` in [engine/pokemon/search.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokemon/search.asm):
```diff
; check OT
-; This only checks five characters, which is fine for the Japanese version,
-; but in the English version the player name is 7 characters, so this is wrong.
ld hl, wPlayerName
-rept NAME_LENGTH_JAPANESE - 2 ; should be PLAYER_NAME_LENGTH - 2
+rept PLAYER_NAME_LENGTH - 2
ld a, [de]
cp [hl]
jr nz, .notfound
cp "@"
jr z, .found ; reached end of string
inc hl
inc de
endr
ld a, [de]
cp [hl]
jr z, .found
```
## Catching a Transformed Pokémon always catches a Ditto
This bug can affect Mew or Pokémon other than Ditto that used Transform via Mirror Move or Sketch.
**Fix:** Edit `PokeBallEffect` in [engine/items/item_effects.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/item_effects.asm):
```diff
ld hl, wEnemySubStatus5
ld a, [hl]
push af
set SUBSTATUS_TRANSFORMED, [hl]
-; This code is buggy. Any wild Pokémon that has Transformed will be
-; caught as a Ditto, even if it was something else like Mew.
-; To fix, do not set [wTempEnemyMonSpecies] to DITTO.
bit SUBSTATUS_TRANSFORMED, a
- jr nz, .ditto
- jr .not_ditto
+ jr nz, .load_data
-.ditto
- ld a, DITTO
- ld [wTempEnemyMonSpecies], a
- jr .load_data
-
-.not_ditto
- set SUBSTATUS_TRANSFORMED, [hl]
ld hl, wEnemyBackupDVs
ld a, [wEnemyMonDVs]
ld [hli], a
ld a, [wEnemyMonDVs + 1]
ld [hl], a
.load_data
ld a, [wTempEnemyMonSpecies]
ld [wCurPartySpecies], a
ld a, [wEnemyMonLevel]
ld [wCurPartyLevel], a
farcall LoadEnemyMon
pop af
ld [wEnemySubStatus5], a
```
## If your party and current PC box are full during the Dude's catching tutorial, his Poké Ball can't be used and may crash the game
([Video](https://www.youtube.com/watch?v=A8zaTOkjKS4&t=407))
**Fix:** Edit `PokeBallEffect` in [engine/items/item_effects.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/item_effects.asm):
```diff
ld a, [wBattleMode]
dec a
jp nz, UseBallInTrainerBattle
+ ld a, [wBattleType]
+ cp BATTLETYPE_TUTORIAL
+ jr z, .room_in_party
+
ld a, [wPartyCount]
cp PARTY_LENGTH
jr nz, .room_in_party
ld a, BANK(sBoxCount)
call GetSRAMBank
ld a, [sBoxCount]
cp MONS_PER_BOX
call CloseSRAM
jp z, Ball_BoxIsFullMessage
```
## Using a Park Ball in normal battles has a corrupt animation
([Video](https://www.youtube.com/watch?v=v1ErZdLCIyU))
**Fix:** Edit `PokeBallEffect` in [engine/items/item_effects.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/item_effects.asm):
```diff
.room_in_party
xor a
ld [wWildMon], a
- ld a, [wCurItem]
- cp PARK_BALL
+ ld a, [wBattleType]
+ cp BATTLETYPE_CONTEST
call nz, ReturnToBattle_UseBall
```
## `HELD_CATCH_CHANCE` has no effect
**Fix:** Edit `PokeBallEffect` in [engine/items/item_effects.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/item_effects.asm):
```diff
- ; BUG: farcall overwrites a, and GetItemHeldEffect takes b anyway.
- ; This is probably the reason the HELD_CATCH_CHANCE effect is never used.
- ; Uncomment the line below to fix.
ld d, a
push de
ld a, [wBattleMonItem]
- ; ld b, a
+ ld b, a
farcall GetItemHeldEffect
ld a, b
cp HELD_CATCH_CHANCE
pop de
ld a, d
jr nz, .max_2
add c
jr nc, .max_2
ld a, $ff
.max_2
```
## Only the first three evolution entries can have Stone compatibility reported correctly
**Workaround:** Edit `PlacePartyMonEvoStoneCompatibility.DetermineCompatibility` in [engine/pokemon/party_menu.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokemon/party_menu.asm):
```diff
.DetermineCompatibility:
ld de, wStringBuffer1
ld a, BANK(EvosAttacksPointers)
ld bc, 2
call FarCopyBytes
ld hl, wStringBuffer1
ld a, [hli]
ld h, [hl]
ld l, a
ld de, wStringBuffer1
ld a, BANK("Evolutions and Attacks")
- ld bc, 10
+ ld bc, wStringBuffer2 - wStringBuffer1
call FarCopyBytes
```
This supports up to six entries.
## `EVOLVE_STAT` can break Stone compatibility reporting
**Fix:** Edit `PlacePartyMonEvoStoneCompatibility.DetermineCompatibility` in [engine/pokemon/party_menu.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokemon/party_menu.asm):
```diff
.loop2
ld a, [hli]
and a
jr z, .nope
+ cp EVOLVE_STAT
+ jr nz, .not_four_bytes
+ inc hl
+.not_four_bytes
inc hl
inc hl
cp EVOLVE_ITEM
jr nz, .loop2
```
## `ScriptCall` can overflow `wScriptStack` and crash
**Fix:** Edit `ScriptCall` in [engine/overworld/scripting.asm](https://github.com/pret/pokecrystal/blob/master/engine/overworld/scripting.asm):
```diff
ScriptCall:
-; Bug: The script stack has a capacity of 5 scripts, yet there is
-; nothing to stop you from pushing a sixth script. The high part
-; of the script address can then be overwritten by modifications
-; to wScriptDelay, causing the script to return to the rst/interrupt
-; space.
-
+ ld hl, wScriptStackSize
+ ld a, [hl]
+ cp 5
+ ret nc
push de
- ld hl, wScriptStackSize
- ld e, [hl]
inc [hl]
+ ld e, a
ld d, 0
ld hl, wScriptStack
add hl, de
add hl, de
add hl, de
pop de
ld a, [wScriptBank]
ld [hli], a
ld a, [wScriptPos]
ld [hli], a
ld a, [wScriptPos + 1]
ld [hl], a
ld a, b
ld [wScriptBank], a
ld a, e
ld [wScriptPos], a
ld a, d
ld [wScriptPos + 1], a
ret
```
## `LoadSpriteGFX` does not limit the capacity of `UsedSprites`
**Fix:** Edit `LoadSpriteGFX` in [engine/overworld/overworld.asm](https://github.com/pret/pokecrystal/blob/master/engine/overworld/overworld.asm):
```diff
LoadSpriteGFX:
-; Bug: b is not preserved, so it's useless as a next count.
-; Uncomment the lines below to fix.
-
ld hl, wUsedSprites
ld b, SPRITE_GFX_LIST_CAPACITY
.loop
ld a, [hli]
and a
jr z, .done
push hl
call .LoadSprite
pop hl
ld [hli], a
dec b
jr nz, .loop
.done
ret
.LoadSprite:
- ; push bc
+ push bc
call GetSprite
- ; pop bc
+ pop bc
ld a, l
ret
```
## `ChooseWildEncounter` doesn't really validate the wild Pokémon species
**Fix:** Edit `ChooseWildEncounter` in [engine/overworld/wildmons.asm](https://github.com/pret/pokecrystal/blob/master/engine/overworld/wildmons.asm):
```diff
.ok
ld a, b
ld [wCurPartyLevel], a
ld b, [hl]
- ; ld a, b
+ ld a, b
call ValidateTempWildMonSpecies
jr c, .nowildbattle
- ld a, b ; This is in the wrong place.
cp UNOWN
jr nz, .done
```
## `TryObjectEvent` arbitrary code execution
**Fix:** Edit `TryObjectEvent` in [engine/overworld/events.asm](https://github.com/pret/pokecrystal/blob/master/engine/overworld/events.asm):
```diff
-; Bug: If IsInArray returns nc, data at bc will be executed as code.
push bc
ld de, 3
ld hl, .pointers
call IsInArray
- jr nc, .nope
pop bc
+ jr nc, .nope
inc hl
ld a, [hli]
ld h, [hl]
ld l, a
jp hl
.nope
- ; pop bc
xor a
ret
```
## `ReadObjectEvents` overflows into `wObjectMasks`
**Fix:** Edit `ReadObjectEvents` in [home/map.asm](https://github.com/pret/pokecrystal/blob/master/home/map.asm):
```diff
-; get NUM_OBJECTS - [wCurMapObjectEventCount]
+; get NUM_OBJECTS - [wCurMapObjectEventCount] - 1
ld a, [wCurMapObjectEventCount]
ld c, a
- ld a, NUM_OBJECTS ; - 1
+ ld a, NUM_OBJECTS - 1
sub c
jr z, .skip
- ; jr c, .skip
+ jr c, .skip
; could have done "inc hl" instead
ld bc, 1
add hl, bc
-; Fill the remaining sprite IDs and y coords with 0 and -1, respectively.
-; Bleeds into wObjectMasks due to a bug. Uncomment the above code to fix.
ld bc, MAPOBJECT_LENGTH
.loop
ld [hl], 0
inc hl
ld [hl], -1
dec hl
add hl, bc
dec a
jr nz, .loop
```
## `ClearWRAM` only clears WRAM bank 1
**Fix:** Edit `ClearWRAM` in [home/init.asm](https://github.com/pret/pokecrystal/blob/master/home/init.asm):
```diff
ClearWRAM::
; Wipe swappable WRAM banks (1-7)
; Assumes CGB or AGB
ld a, 1
.bank_loop
push af
ldh [rSVBK], a
xor a
ld hl, WRAM1_Begin
ld bc, WRAM1_End - WRAM1_Begin
call ByteFill
pop af
inc a
cp 8
- jr nc, .bank_loop ; Should be jr c
+ jr c, .bank_loop
ret
```
## `BattleAnimCmd_ClearObjs` only clears the first 6⅔ objects
**Fix:** Edit `BattleAnimCmd_ClearObjs` in [engine/battle_anims/anim_commands.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle_anims/anim_commands.asm):
```diff
BattleAnimCmd_ClearObjs:
-; BUG: This function only clears the first 6⅔ objects
ld hl, wActiveAnimObjects
- ld a, $a0 ; should be NUM_ANIM_OBJECTS * BATTLEANIMSTRUCT_LENGTH
+ ld a, NUM_ANIM_OBJECTS * BATTLEANIMSTRUCT_LENGTH
.loop
ld [hl], 0
inc hl
dec a
jr nz, .loop
ret
```