ref: 747c9059d4912c275d3e1e708c026b1fe61e3b42
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. ## Contents - [Thick Club and Light Ball can decrease damage done with boosted (Special) Attack](#thick-club-and-light-ball-can-decrease-damage-done-with-boosted-special-attack) - [Metal Powder can increase damage taken with boosted (Special) Defense](#metal-powder-can-increase-damage-taken-with-boosted-special-defense) - [Belly Drum sharply boosts Attack even with under 50% HP](#belly-drum-sharply-boosts-attack-even-with-under-50-hp) - [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) - [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) - [Beat Up can desynchronize link battles](#beat-up-can-desynchronize-link-battles) - [Present damage is incorrect in link battles](#present-damage-is-incorrect-in-link-battles) - ["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) - [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) - [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) - [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) - [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) - [`Function6ec1` does not correctly limit object movement](#function6ec1-does-not-correctly-limit-object-movement) - [`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) - [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 `EvosAttacks` evolution entries can have Stone compatibility reported correctly](#only-the-first-three-evosattacks-evolution-entries-can-have-stone-compatibility-reported-correctly) - [`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) - [`Special_CheckBugContestContestantFlag` can read beyond its data table](#special_checkbugcontestcontestantflag-can-read-beyond-its-data-table) - [`ClearWRAM` only clears WRAM bank 1](#clearwram-only-clears-wram-bank-1) ## Thick Club and Light Ball can decrease damage done with boosted (Special) Attack *Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.* ([Video](https://www.youtube.com/watch?v=rGqu3d3pdok&t=450)) This is a bug with `SpeciesItemBoost` in [engine/battle/effect_commands.asm](/engine/battle/effect_commands.asm): ```asm ; Double the stat sla l rl h ret ``` **Fix:** ```asm ; Double the stat sla l rl h ld a, HIGH(MAX_STAT_VALUE) cp h jr c, .cap ld a, LOW(MAX_STAT_VALUE) cp l ret nc .cap ld h, HIGH(MAX_STAT_VALUE) ld l, LOW(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)) This is a bug with `DittoMetalPowder` in [engine/battle/effect_commands.asm](/engine/battle/effect_commands.asm): ```asm 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 ret ``` **Fix:** ```asm 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 ld a, LOW(MAX_STAT_VALUE) cp c ret nc .cap ld b, HIGH(MAX_STAT_VALUE) ld c, LOW(MAX_STAT_VALUE) ret ``` ## 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)) This is a bug with `BattleCommand_BellyDrum` in [engine/battle/effect_commands.asm](/engine/battle/effect_commands.asm): ```asm BattleCommand_BellyDrum: ; 37c1a ; 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, [AttackMissed] and a jr nz, .failed callab GetHalfMaxHP callab CheckUserHasEnoughHP jr nc, .failed ``` **Fix:** ```asm BattleCommand_BellyDrum: ; 37c1a ; bellydrum callab GetHalfMaxHP callab CheckUserHasEnoughHP jr nc, .failed call BattleCommand_AttackUp2 ld a, [AttackMissed] and a jr nz, .failed ``` ## 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)) *To do:* Identify specific code causing this bug and fix it. ## 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. This is a bug with `DefenseDownHit` in [data/moves/effects.asm](/data/moves/effects.asm): ```asm DefenseDownHit: checkobedience usedmovetext doturn critical damagestats damagecalc stab damagevariation checkhit effectchance hittarget failuretext checkfaint criticaltext supereffectivetext checkdestinybond buildopponentrage effectchance ; bug: duplicate effectchance shouldn't be here defensedown statdownmessage endmove ``` **Fix:** Delete the second `effectchance`. ## 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)) *To do:* Identify specific code causing this bug and fix it. ## 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)) This is a bug with `CheckPlayerHasUsableMoves` in [engine/battle/core.asm](/engine/battle/core.asm): ```asm .done ; Bug: this will result in a move with PP Up confusing the game. ; Replace with "and $3f" to fix. and a ret nz .force_struggle ld hl, BattleText_PkmnHasNoMovesLeft call StdBattleTextBox ld c, 60 call DelayFrames xor a ret ``` **Fix:** Change `and a` to `and $3f`. ## 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)) *To do:* Identify specific code causing this bug and fix it. ## 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. This is a bug with `CheckHiddenOpponent` in [engine/battle/effect_commands.asm](/engine/battle/effect_commands.asm): ```asm CheckHiddenOpponent: ; 37daa ; BUG: This routine should account for Lock-On and Mind Reader. ld a, BATTLE_VARS_SUBSTATUS3_OPP call GetBattleVar and 1 << SUBSTATUS_FLYING | 1 << SUBSTATUS_UNDERGROUND ret ``` *To do:* Fix this bug. ## 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)) This is a bug with `BattleCommand_BeatUp` in [engine/battle/effect_commands.asm](/engine/battle/effect_commands.asm): ```asm .got_mon ld a, [wd002] ld hl, PartyMonNicknames 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, [CurBattleMon] ; BUG: this can desynchronize link battles ; Change "cp [hl]" to "cp c" to fix cp [hl] ld hl, BattleMonStatus jr z, .active_mon ld a, MON_STATUS call GetBeatupMonLocation .active_mon ld a, [hl] and a jp nz, .beatup_fail ``` **Fix:** Change `cp [hl]` to `cp c`. ## 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. This is a bug with `BattleCommand_Present` in [engine/battle/effect_commands/present.asm](/engine/battle/effect_commands/present.asm): ```asm BattleCommand_Present: ; 37874 ; 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 ``` **Fix:** ```asm BattleCommand_Present: ; 37874 ; present push bc push de call BattleCommand_Stab pop de pop bc ``` ## "Smart" AI encourages Mean Look if its own Pokémon is badly poisoned ([Video](https://www.youtube.com/watch?v=cygMO-zHTls)) This is a bug with `AI_Smart_MeanLook` in [engine/battle/ai/scoring.asm](/engine/battle/ai/scoring.asm): ```asm ; 80% chance to greatly encourage this move if the enemy is badly poisoned (buggy). ; Should check PlayerSubStatus5 instead. ld a, [EnemySubStatus5] bit SUBSTATUS_TOXIC, a jr nz, .asm_38e26 ``` **Fix:** Change `EnemySubStatus5` to `PlayerSubStatus5`. ## AI makes a false assumption about `CheckTypeMatchup` In [engine/battle/effect_commands.asm](/engine/battle/effect_commands.asm): ```asm BattleCheckTypeMatchup: ; 347c8 ld hl, EnemyMonType1 ld a, [hBattleTurn] and a jr z, CheckTypeMatchup ld hl, BattleMonType1 CheckTypeMatchup: ; 347d3 ; 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 ``` *To do:* Fix this bug. ## NPC use of Full Heal or Full Restore does not cure Nightmare status ([Video](https://www.youtube.com/watch?v=rGqu3d3pdok&t=322)) This is a bug with `AI_HealStatus` in [engine/battle/ai/items.asm](/engine/battle/ai/items.asm): ```asm AI_HealStatus: ; 384e0 ld a, [CurOTMon] ld hl, OTPartyMon1Status ld bc, PARTYMON_STRUCT_LENGTH call AddNTimes xor a ld [hl], a ld [EnemyMonStatus], a ; Bug: this should reset SUBSTATUS_NIGHTMARE too ; Uncomment the lines below to fix ; ld hl, EnemySubStatus1 ; res SUBSTATUS_NIGHTMARE, [hl] ld hl, EnemySubStatus5 res SUBSTATUS_TOXIC, [hl] ret ; 384f7 ``` **Fix:** Uncomment `ld hl, EnemySubStatus1` and `res SUBSTATUS_NIGHTMARE, [hl]`. ## HP bar animation is slow for high HP ([Video](https://www.youtube.com/watch?v=SE-BfsFgZVM)) This is a bug with `LongAnim_UpdateVariables` in [engine/battle/anim_hp_bar.asm](/engine/battle/anim_hp_bar.asm): ```asm ; 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 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 ``` **Fix:** Move `ld a, e` to right after `call ComputeHPBarPixels`. ## HP bar animation off-by-one error for low HP ([Video](https://www.youtube.com/watch?v=9KyNVIZxJvI)) This is a bug with `ShortHPBar_CalcPixelFrame` in [engine/anim_hp_bar.asm](/engine/anim_hp_bar.asm): ```asm ld b, 0 ; This routine is buggy. If [wCurHPAnimMaxHP] * [wCurHPBarPixels] is divisible ; by 48, the loop runs one extra time. To fix, uncomment the line below. .loop ld a, l sub 6 * 8 ld l, a ld a, h sbc $0 ld h, a ; jr z, .done jr c, .done inc b jr .loop ``` **Fix:** Uncomment `jr z, .done`. ## 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. This is a bug with `CalcExpAtLevel` in [main.asm](/main.asm): ```asm CalcExpAtLevel: ; 50e47 ; (a/b)*n**3 + c*n**2 + d*n - e ld a, [BaseGrowthRate] add a add a ld c, a ld b, 0 ld hl, GrowthRates add hl, bc ``` **Fix:** ```asm CalcExpAtLevel: ; 50e47 ; (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, [BaseGrowthRate] 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)) This is a bug with `Text_ABoostedStringBuffer2ExpPoints` and `Text_StringBuffer2ExpPoints` in [text/common_2.asm](/text/common_2.asm): ```asm Text_ABoostedStringBuffer2ExpPoints:: text_start line "a boosted" cont "@" deciram StringBuffer2, 2, 4 text " EXP. Points!" prompt Text_StringBuffer2ExpPoints:: text_start line "@" deciram StringBuffer2, 2, 4 text " EXP. Points!" prompt ``` **Fix:** Change both `deciram StringBuffer2, 2, 4` to `deciram StringBuffer2, 2, 5`. ## BRN/PSN/PAR do not affect catch rate This is a bug with `PokeBall` in [items/item_effects.asm](/items/item_effects.asm): ```asm .statuscheck ; 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, [EnemyMonStatus] and 1 << FRZ | SLP ld c, 10 jr nz, .addstatus ; ld a, [EnemyMonStatus] 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 ``` **Fix:** Uncomment `ld a, [EnemyMonStatus]`. ## Moon Ball does not boost catch rate This is a bug with `MoonBallMultiplier` in [items/item_effects.asm](/items/item_effects.asm): ```asm MoonBallMultiplier: ; This function is buggy. ; Intent: multiply catch rate by 4 if mon evolves with moon stone ; Reality: no boost ... ; 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(EvosAttacks) call GetFarByte cp MOON_STONE_RED ; BURN_HEAL pop bc ret nz ``` **Fix:** Change `MOON_STONE_RED` to `MOON_STONE`. ## Love Ball boosts catch rate for the wrong gender This is a bug with `LoveBallMultiplier` in [items/item_effects.asm](/items/item_effects.asm): ```asm LoveBallMultiplier: ; This function is buggy. ; Intent: multiply catch rate by 8 if mons are of same species, different sex ; Reality: multiply catch rate by 8 if mons are of same species, same sex ... ld a, d pop de cp d pop bc ret nz ; for the intended effect, this should be "ret z" ``` **Fix:** Change `ret nz` to `ret z`. ## Fast Ball only boosts catch rate for three Pokémon This is a bug with `FastBallMultiplier` in [items/item_effects.asm](/items/item_effects.asm): ```asm FastBallMultiplier: ; This function is buggy. ; Intent: multiply catch rate by 4 if enemy mon is in one of the three ; FleeMons tables. ; Reality: multiply catch rate by 4 if enemy mon is one of the first three in ; the first FleeMons table. ... inc hl cp -1 jr z, .next cp c jr nz, .next ; for the intended effect, this should be "jr nz, .loop" sla b jr c, .max ``` **Fix:** Change `jr nz, .next` to `jr nz, .loop`. ## Dragon Scale, not Dragon Fang, boosts Dragon-type moves *Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.* This is a bug with `ItemAttributes` in [items/attributes.asm](/items/attributes.asm): ```asm ; DRAGON FANG item_attribute 100, 0, 0, CANT_SELECT, ITEM, ITEMMENU_NOUSE, ITEMMENU_NOUSE ... ; DRAGON SCALE item_attribute 2100, HELD_DRAGON_BOOST, 10, CANT_SELECT, ITEM, ITEMMENU_NOUSE, ITEMMENU_NOUSE ``` **Fix:** Move `HELD_DRAGON_BOOST` to the `DRAGON FANG` attributes and `0` to `DRAGON SCALE`. ## Daisy's grooming doesn't always increase happiness This is a bug with `MassageOrHaircut` in [engine/events/special.asm](/engine/events/special.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 massage 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 [ScriptVar], a ld c, [hl] call ChangeHappiness ret ... Data_DaisyMassage: ; 746b db $ff, 2, HAPPINESS_MASSAGE ; 99.6% chance CopyPokemonName_Buffer1_Buffer3: ; 746e ld hl, StringBuffer1 ld de, StringBuffer3 ld bc, PKMN_NAME_LENGTH jp CopyBytes ``` **Fix:** ```asm Data_DaisyMassage: ; 746b db $80, 2, HAPPINESS_MASSAGE ; 50% chance db $ff, 2, HAPPINESS_MASSAGE ; 50% chance ``` ## Magikarp in Lake of Rage are shorter, not longer This is a bug with `LoadEnemyMon.CheckMagikarpArea` in [engine/battle/core.asm](/engine/battle/core.asm): ```asm .CheckMagikarpArea: ; The z checks are supposed to be 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 size flooring in the Lake of Rage area ld a, [MapGroup] cp GROUP_LAKE_OF_RAGE jr z, .Happiness ld a, [MapNumber] cp MAP_LAKE_OF_RAGE jr z, .Happiness ``` **Fix:** Change both `jr z, .Happiness` to `jr nz, .Happiness`. ## Magikarp length limits have a unit conversion error This is a bug with `LoadEnemyMon.CheckMagikarpArea` in [engine/battle/core.asm](/engine/battle/core.asm): ```asm ; Get Magikarp's length ld de, EnemyMonDVs ld bc, PlayerID callfar CalcMagikarpLength ; No reason to keep going if length > 1536 (i.e. if length / 256 != 6) ld a, [wMagikarpLength] cp HIGH(1536) ; this compares to 6'0'', should be cp 5 jr nz, .CheckMagikarpArea ; 5% chance of skipping both size checks call Random cp 5 percent jr c, .CheckMagikarpArea ; Try again if length > 1615 ld a, [wMagikarpLength + 1] cp LOW(1616) ; this compares to 6'80'', should be cp 3 jr nc, .GenerateDVs ; 20% chance of skipping this check call Random cp 20 percent - 1 jr c, .CheckMagikarpArea ; Try again if length > 1599 ld a, [wMagikarpLength + 1] cp LOW(1600) ; this compares to 6'64'', should be cp 2 jr nc, .GenerateDVs ``` **Fix:** Change the three `cp` instructions to use their commented values. ## Magikarp lengths can be miscalculated This is a bug with `CalcMagikarpLength.BCLessThanDE` in [engine/events/magikarp.asm](/engine/events/magikarp.asm): ```asm .BCLessThanDE: ; fbc9a ; Intention: Return bc < de. ; Reality: Return b < d. ld a, b cp d ret c ret nc ; whoops ld a, c cp e ret ; fbca1 ``` **Fix:** Delete `ret nc`. ## Battle transitions fail to account for the enemy's level ([Video](https://www.youtube.com/watch?v=eij_1060SMc)) This is a bug with `StartTrainerBattle_DetermineWhichAnimation` in [engine/battle_start.asm](/engine/battle_start.asm): ```asm StartTrainerBattle_DetermineWhichAnimation: ; 8c365 (23:4365) ; The screen flashes a different number of times depending on the level of ; your lead Pokemon relative to the opponent's. ; BUG: BattleMonLevel and EnemyMonLevel are not set at this point, so whatever ; values happen to be there will determine the animation. ld de, 0 ld a, [BattleMonLevel] add 3 ld hl, EnemyMonLevel cp [hl] jr nc, .okay set 0, e .okay ld a, [wPermission] cp CAVE jr z, .okay2 cp PERM_5 jr z, .okay2 cp DUNGEON jr z, .okay2 set 1, e .okay2 ld hl, .StartingPoints add hl, de ld a, [hl] ld [wJumptableIndex], a ret ; 8c38f (23:438f) .StartingPoints: ; 8c38f db 1, 9 db 16, 24 ; 8c393 ``` *To do:* Fix this bug. ## Slot machine payout sound effects cut each other off ([Video](https://www.youtube.com/watch?v=ojq3xqfRF6I)) This is a bug with `Slots_PayoutAnim` in [engine/slot_machine.asm](/engine/slot_machine.asm): ```asm .okay ld [hl], e dec hl ld [hl], d ld a, [wcf64] and $7 ret z ; ret nz would be more appropriate ld de, SFX_GET_COIN_FROM_SLOTS call PlaySFX ret ``` **Fix:** Change `ret z` to `ret nz`. ## Team Rocket battle music is not used for Executives or Scientists This is a bug with `PlayBattleMusic` in [main.asm](/main.asm): ```asm ; really, they should have included admins and scientists here too... ld de, MUSIC_ROCKET_BATTLE cp GRUNTM jr z, .done cp GRUNTF jr z, .done ``` **Fix:** ```asm 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` This is a bug with `DoPlayerMovement.CheckWarp` in [engine/player_movement.asm](/engine/player_movement.asm): ```asm ; Bug: Since no case is made for STANDING here, it will check ; [.edgewarps + $ff]. This resolves to $3e at $8035a. ; This causes wd041 to be nonzero when standing on tile $3e, ; making bumps silent. ld a, [WalkingDirection] ; cp STANDING ; jr z, .not_warp ld e, a ld d, 0 ld hl, .EdgeWarps add hl, de ld a, [PlayerStandingTile] cp [hl] jr nz, .not_warp ld a, 1 ld [wd041], a ld a, [WalkingDirection] ; This is in the wrong place. cp STANDING jr z, .not_warp ``` **Fix:** ```asm ld a, [WalkingDirection] cp STANDING jr z, .not_warp ld e, a ld d, 0 ld hl, .EdgeWarps add hl, de ld a, [PlayerStandingTile] cp [hl] jr nz, .not_warp ld a, 1 ld [wd041], a ld a, [WalkingDirection] ``` ## Playing Entei's Pokédex cry can distort Raikou's and Suicune's ([Video](https://www.youtube.com/watch?v=z305e4sIO24)) The exact cause is unknown, but a workaround exists for `DexEntryScreen_MenuActionJumptable.Cry` in [engine/pokedex.asm](/engine/pokedex.asm): ```asm .Cry: ; 40340 call Pokedex_GetSelectedMon ld a, [wd265] call GetCryIndex ld e, c ld d, b call PlayCry ret ``` **Workaround:** ```asm .Cry: ; 40340 ld a, [CurPartySpecies] call PlayMonCry ret ``` ## In-battle “`…`” ellipsis is too high This is a mistake with the “`…`” tile in [gfx/battle/hp_exp_bar_border.png](/gfx/battle/hp_exp_bar_border.png):  **Fix:** Lower the ellipsis by two pixels:  ## 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](/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. In [home/map.asm](/home/map.asm): ```asm ; Set hl to the address of the current metatile data ([TilesetBlocksAddress] + (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 ld a, [TilesetBlocksAddress] add l ld l, a ld a, [TilesetBlocksAddress + 1] adc h ld h, a ``` **Fix:** Delete `add a` and uncomment `add hl, hl`. ## Surfing directly across a map connection does not load the new map ([Video](https://www.youtube.com/watch?v=XFOWvMNG-zw)) *To do:* Identify specific code causing this bug and fix it. ## `Function6ec1` does not correctly limit object movement This bug is why the Lapras in Union Cave, which uses `SPRITEMOVEDATA_LAPRAS`, is not restricted by its `1, 1` movement radius. In [engine/npc_movement.asm](/engine/npc_movement.asm): ```asm ld hl, OBJECT_FLAGS1 add hl, bc bit 4, [hl] ; lost, uncomment next line to fix ; jr nz, .resume ``` **Fix:** Uncomment `jr nz, .resume`. ## `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. In [engine/search.asm](/engine/search.asm): ```asm ; 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, PlayerName rept NAME_LENGTH_JAPANESE +- 2 ; should be 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 .notfound pop de pop hl pop bc and a ret ``` **Fix:** Change `rept NAME_LENGTH_JAPANESE +- 2` to `rept PLAYER_NAME_LENGTH +- 2`. ## 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. This is a bug with `PokeBall` in [items/item_effects.asm](/items/item_effects.asm): ```asm ld hl, EnemySubStatus5 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 [TempEnemyMonSpecies] to DITTO. bit SUBSTATUS_TRANSFORMED, a jr nz, .ditto jr .not_ditto .ditto ld a, DITTO ld [TempEnemyMonSpecies], a jr .load_data .not_ditto set SUBSTATUS_TRANSFORMED, [hl] ld hl, wEnemyBackupDVs ld a, [EnemyMonDVs] ld [hli], a ld a, [EnemyMonDVs + 1] ld [hl], a .load_data ld a, [TempEnemyMonSpecies] ld [CurPartySpecies], a ld a, [EnemyMonLevel] ld [CurPartyLevel], a callba LoadEnemyMon pop af ld [EnemySubStatus5], a ``` **Fix:** ```asm ld hl, EnemySubStatus5 ld a, [hl] push af set SUBSTATUS_TRANSFORMED, [hl] bit SUBSTATUS_TRANSFORMED, a jr nz, .load_data ld hl, wEnemyBackupDVs ld a, [EnemyMonDVs] ld [hli], a ld a, [EnemyMonDVs + 1] ld [hl], a .load_data ld a, [TempEnemyMonSpecies] ld [CurPartySpecies], a ld a, [EnemyMonLevel] ld [CurPartyLevel], a callba LoadEnemyMon pop af ld [EnemySubStatus5], a ``` ## Using a Park Ball in normal battles has a corrupt animation ([Video](https://www.youtube.com/watch?v=v1ErZdLCIyU)) This is a bug with `ParkBall` in [items/item_effects.asm](/items/item_effects.asm): ```asm .room_in_party xor a ld [wWildMon], a ld a, [CurItem] cp PARK_BALL call nz, ReturnToBattle_UseBall ``` **Fix:** ```asm .room_in_party xor a ld [wWildMon], a ld a, [BattleType] cp BATTLETYPE_CONTEST call nz, ReturnToBattle_UseBall ``` ## `HELD_CATCH_CHANCE` has no effect This is a bug with `PokeBall` in [items/item_effects.asm](/items/item_effects.asm): ```asm ; BUG: callba 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 a, [BattleMonItem] ; ld b, a callba GetItemHeldEffect ld a, b cp HELD_CATCH_CHANCE ``` **Fix:** Uncomment `ld b, a`. ## Only the first three `EvosAttacks` evolution entries can have Stone compatibility reported correctly This is a bug with `PlacePartyMonEvoStoneCompatibility.DetermineCompatibility` in [engine/party_menu.asm](/engine/party_menu.asm): ```asm .DetermineCompatibility: ; 50268 ld de, StringBuffer1 ld a, BANK(EvosAttacksPointers) ld bc, 2 call FarCopyBytes ld hl, StringBuffer1 ld a, [hli] ld h, [hl] ld l, a ld de, StringBuffer1 ld a, BANK(EvosAttacks) ld bc, $a call FarCopyBytes ``` **Fix:** Change `ld bc, $a` to `ld bc, $10` to support up to five Stone entries. ## `ScriptCall` can overflow `wScriptStack` and crash In [engine/scripting.asm](/engine/scripting.asm): ```asm 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 ScriptDelay, causing the script to return to the rst/interrupt ; space. push de ld hl, wScriptStackSize ld e, [hl] inc [hl] ld d, $0 ld hl, wScriptStack add hl, de add hl, de add hl, de pop de ld a, [ScriptBank] ld [hli], a ld a, [ScriptPos] ld [hli], a ld a, [ScriptPos + 1] ld [hl], a ld a, b ld [ScriptBank], a ld a, e ld [ScriptPos], a ld a, d ld [ScriptPos + 1], a ret ``` ## `LoadSpriteGFX` does not limit the capacity of `UsedSprites` In [engine/overworld.asm](/engine/overworld.asm): ```asm LoadSpriteGFX: ; 14306 ; Bug: b is not preserved, so it's useless as a next count. ; Uncomment the lines below to fix. ld hl, UsedSprites 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 call GetSprite ; pop bc ld a, l ret ; 1431e ``` **Fix:** Uncomment `push bc` and `pop bc`. ## `ChooseWildEncounter` doesn't really validate the wild Pokémon species In [engine/wildmons.asm](/engine/wildmons.asm): ```asm ChooseWildEncounter: ; 2a14f ... ld a, b ld [CurPartyLevel], a ld b, [hl] ; ld a, b call ValidateTempWildMonSpecies jr c, .nowildbattle ld a, b ; This is in the wrong place. cp UNOWN jr nz, .done ... ValidateTempWildMonSpecies: ; 2a4a0 ; Due to a development oversight, this function is called with the wild Pokemon's level, not its species, in a. ``` **Fix:** ```asm ld a, b ld [CurPartyLevel], a ld b, [hl] ld a, b call ValidateTempWildMonSpecies jr c, .nowildbattle cp UNOWN jr nz, .done ``` ## `TryObjectEvent` arbitrary code execution In [engine/events.asm](/engine/events.asm): ```asm ; 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_bugged pop bc inc hl ld a, [hli] ld h, [hl] ld l, a jp hl .nope_bugged ; pop bc xor a ret ``` **Fix:** Uncomment `pop bc`. ## `Special_CheckBugContestContestantFlag` can read beyond its data table In [engine/events/bug_contest/contest_2.asm](/engine/events/bug_contest/contest_2.asm): ```asm Special_CheckBugContestContestantFlag: ; 139ed ; Checks the flag of the Bug Catching Contestant whose index is loaded in a. ; Bug: If a >= 10 when this is called, it will read beyond the table. ld hl, BugCatchingContestantEventFlagTable ld e, a ld d, 0 add hl, de add hl, de ld e, [hl] inc hl ld d, [hl] ld b, CHECK_FLAG call EventFlagAction ret ; 139fe BugCatchingContestantEventFlagTable: ; 139fe dw EVENT_BUG_CATCHING_CONTESTANT_1A dw EVENT_BUG_CATCHING_CONTESTANT_2A dw EVENT_BUG_CATCHING_CONTESTANT_3A dw EVENT_BUG_CATCHING_CONTESTANT_4A dw EVENT_BUG_CATCHING_CONTESTANT_5A dw EVENT_BUG_CATCHING_CONTESTANT_6A dw EVENT_BUG_CATCHING_CONTESTANT_7A dw EVENT_BUG_CATCHING_CONTESTANT_8A dw EVENT_BUG_CATCHING_CONTESTANT_9A dw EVENT_BUG_CATCHING_CONTESTANT_10A ; 13a12 ``` ## `ClearWRAM` only clears WRAM bank 1 In [home/init.asm](/home/init.asm): ```asm ClearWRAM:: ; 25a ; Wipe swappable WRAM banks (1-7) ; Assumes CGB or AGB ld a, 1 .bank_loop push af ld [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 ret ; 270 ``` **Fix:** Change `jr nc, .bank_loop` to `jr c, .bank_loop`.