ref: d4025863cf56466b79827bace6d6b3e48ffd05e9
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) - [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) - ["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) - [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) - [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) - [`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) - [`CheckBugContestContestantFlag` can read beyond its data table](#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/move_effects/belly_drum.asm](/engine/battle/move_effects/belly_drum.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, [wAttackMissed] and a jr nz, .failed callfar GetHalfMaxHP callfar CheckUserHasEnoughHP jr nc, .failed ``` **Fix:** ```asm BattleCommand_BellyDrum: ; 37c1a ; bellydrum callfar GetHalfMaxHP callfar CheckUserHasEnoughHP jr nc, .failed call BattleCommand_AttackUp2 ld a, [wAttackMissed] 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. and a ; should be "and PP_MASK" ret nz .force_struggle ld hl, BattleText_MonHasNoMovesLeft call StdBattleTextBox ld c, 60 call DelayFrames xor a ret ``` **Fix:** Change `and a` to `and PP_MASK`. ## 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/move_effects/beat_up.asm](/engine/battle/move_effects/beat_up.asm): ```asm .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] ld hl, wBattleMonStatus 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`. ## Beat Up may fail to raise substitute *Fixing this bug will break compatibility with standard Pokémon Crystal for link battles.* (Only the fixes denoted with "breaking" will actually break compatibility, the others just affect what's shown on the screen with the patched game) This is a bug in `BattleCommand_EndLoop` in [engine/battle/effect_commands.asm](/engine/battle/effect_commands.asm) that prevents the rest of the move's effect from being executed if the player or enemy only has one mon in their party while using Beat Up. It prevents the substitute from being raised and the King's Rock from working. ```asm .only_one_beatup ld a, BATTLE_VARS_SUBSTATUS3 call GetBattleVarAddr res SUBSTATUS_IN_LOOP, [hl] call BattleCommand_BeatUpFailText jp EndMoveEffect ``` **Fix (breaking):** Replace the last two lines with `ret`. **Fix (cosmetics):** Call `BattleCommand_RaiseSub` before the `jp`. There's a similar oversight in `BattleCommand_FailureText` in [engine/battle/effect_commands.asm](/engine/battle/effect_commands.asm) that will prevent the substitute from being raised if Beat Up is protected against. ```asm cp EFFECT_MULTI_HIT jr z, .multihit cp EFFECT_DOUBLE_HIT jr z, .multihit cp EFFECT_POISON_MULTI_HIT jr z, .multihit jp EndMoveEffect .multihit call BattleCommand_RaiseSub jp EndMoveEffect ``` **Fix:** Check for `EFFECT_BEAT_UP` as well. ## 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 is a bug in how `wAttackMissed` is never set by BeatUp, even when none of the 'mon have been able to attack (due to being fainted or having a status effect), the King's Rock may activate. This bug can be fixed in a plethora of ways, but the most straight-forward would be in `BattleCommand_BeatUpFailText` in [engine/battle/move_effects/beat_up.asm](/engine/battle/move_effects/beat_up.asm), as that's always ran before the king's rock effect. ```asm BattleCommand_BeatUpFailText: ; 355b5 ; beatupfailtext ld a, [wBeatUpHitAtLeastOnce] and a ret nz jp PrintButItFailed ``` **Fix:** ```asm BattleCommand_BeatUpFailText: ; 355b5 ; 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. This is a bug with `BattleCommand_Present` in [engine/battle/move_effects/present.asm](/engine/battle/move_effects/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 wPlayerSubStatus5 instead. ld a, [wEnemySubStatus5] bit SUBSTATUS_TOXIC, a jr nz, .asm_38e26 ``` **Fix:** Change `wEnemySubStatus5` to `wPlayerSubStatus5`. ## AI makes a false assumption about `CheckTypeMatchup` In [engine/battle/effect_commands.asm](/engine/battle/effect_commands.asm): ```asm BattleCheckTypeMatchup: ; 347c8 ld hl, wEnemyMonType1 ld a, [hBattleTurn] and a jr z, CheckTypeMatchup ld hl, wBattleMonType1 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, [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 too ; Uncomment the lines below to fix ; ld hl, wEnemySubStatus1 ; res SUBSTATUS_NIGHTMARE, [hl] ld hl, wEnemySubStatus5 res SUBSTATUS_TOXIC, [hl] ret ; 384f7 ``` **Fix:** Uncomment `ld hl, wEnemySubStatus1` 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 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 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 [engine/experience.asm](/engine/experience.asm): ```asm CalcExpAtLevel: ; 50e47 ; (a/b)*n**3 + c*n**2 + d*n - e ld a, [wBaseGrowthRate] 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, [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)) This is a bug with `Text_ABoostedStringBuffer2ExpPoints` and `Text_StringBuffer2ExpPoints` in [data/text/common_2.asm](/data/text/common_2.asm): ```asm Text_ABoostedStringBuffer2ExpPoints:: text_start line "a boosted" cont "@" deciram wStringBuffer2, 2, 4 text " EXP. Points!" prompt Text_StringBuffer2ExpPoints:: text_start line "@" deciram wStringBuffer2, 2, 4 text " EXP. Points!" prompt ``` **Fix:** Change both `deciram wStringBuffer2, 2, 4` to `deciram wStringBuffer2, 2, 5`. ## BRN/PSN/PAR do not affect catch rate This is a bug with `PokeBallEffect` in [engine/item_effects.asm](/engine/item_effects.asm): ```asm ; 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] 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, [wEnemyMonStatus]`. ## 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 [data/items/attributes.asm](/data/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 `HaircutOrGrooming` in [engine/events/specials_2.asm](/engine/events/specials_2.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: ; 746e ld hl, wStringBuffer1 ld de, wStringBuffer3 ld bc, MON_NAME_LENGTH jp CopyBytes ``` In [data/events/happiness_probabilities.asm](/data/events/happiness_probabilities.asm): ```asm HappinessData_DaisysGrooming: ; 746b db $ff, 2, HAPPINESS_GROOMING ; 99.6% chance ``` **Fix:** ```asm HappinessData_DaisysGrooming: ; 746b db $80, 2, HAPPINESS_GROOMING ; 50% chance db $ff, 2, HAPPINESS_GROOMING ; 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 "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 ld a, [wMapNumber] 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, 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 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) >= 3 inches) ld a, [wMagikarpLength + 1] cp LOW(1616) ; should be "cp 3", since 1616 mm = 5'3", but LOW(1616) = 80 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) >= 2 inches) ld a, [wMagikarpLength + 1] cp LOW(1600) ; should be "cp 2", since 1600 mm = 5'2", but LOW(1600) = 64 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/battle_transition.asm](/engine/battle/battle_transition.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: wBattleMonLevel and wEnemyMonLevel are not set at this point, so whatever ; values happen to be there will determine the animation. ld de, 0 ld a, [wBattleMonLevel] add 3 ld hl, wEnemyMonLevel cp [hl] jr nc, .okay set 0, e .okay ld a, [wEnvironment] cp CAVE jr z, .okay2 cp ENVIRONMENT_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. ## A "HOF Master!" title for 200-Time Famers is defined but inaccessible ([Video](https://www.youtube.com/watch?v=iHkWubvxmSg)) This is a bug with `_HallOfFamePC.DisplayMonAndStrings` in [engine/events/halloffame.asm](/engine/events/halloffame.asm): ```asm ld a, [wHallOfFameTempWinCount] cp HOF_MASTER_COUNT + 1 ; should be HOF_MASTER_COUNT jr c, .print_num_hof ld de, .HOFMaster hlcoord 1, 2 call PlaceString hlcoord 13, 2 jr .finish ``` **Fix:** Change `HOF_MASTER_COUNT + 1` to `HOF_MASTER_COUNT`. ## 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, [wSlotsDelay] 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 [engine/battle/start_battle.asm](/engine/battle/start_battle.asm): ```asm ; They should have included EXECUTIVEM, EXECUTIVEF, and SCIENTIST 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, [wWalkingDirection] ; 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, 1 ld [wd041], a ld a, [wWalkingDirection] ; This is in the wrong place. cp STANDING jr z, .not_warp ``` **Fix:** ```asm ld a, [wWalkingDirection] 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, 1 ld [wd041], a ld a, [wWalkingDirection] ``` ## 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/pokedex.asm](/engine/pokedex/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 ([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 ld a, [wTilesetBlocksAddress] add l ld l, a ld a, [wTilesetBlocksAddress + 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 [maps/UnionCaveB2F.asm](/maps/UnionCaveB2F.asm), which uses `SPRITEMOVEDATA_SWIM_WANDER`, 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, wPlayerName 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 ``` **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 `PokeBallEffect` in [engine/item_effects.asm](/engine/item_effects.asm): ```asm 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 .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 ``` **Fix:** ```asm ld hl, wEnemySubStatus5 ld a, [hl] push af set SUBSTATUS_TRANSFORMED, [hl] bit SUBSTATUS_TRANSFORMED, a jr nz, .load_data 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 ``` ## Using a Park Ball in normal battles has a corrupt animation ([Video](https://www.youtube.com/watch?v=v1ErZdLCIyU)) This is a bug with `PokeBallEffect` in [engine/item_effects.asm](/engine/item_effects.asm): ```asm .room_in_party xor a ld [wWildMon], a ld a, [wCurItem] cp PARK_BALL call nz, ReturnToBattle_UseBall ``` **Fix:** ```asm .room_in_party xor a ld [wWildMon], a ld a, [wBattleType] cp BATTLETYPE_CONTEST call nz, ReturnToBattle_UseBall ``` ## `HELD_CATCH_CHANCE` has no effect This is a bug with `PokeBallEffect` in [engine/item_effects.asm](/engine/item_effects.asm): ```asm ; 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 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 ``` **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, 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(EvosAttacks) ld bc, 10 call FarCopyBytes ``` **Fix:** Change `ld bc, 10` to `ld bc, wStringBuffer2 - wStringBuffer1` to support up to six Stone entries. ## `EVOLVE_STAT` can break Stone compatibility reporting This is a bug with `PlacePartyMonEvoStoneCompatibility.DetermineCompatibility` in [engine/party_menu.asm](/engine/party_menu.asm): ```asm .loop2 ld a, [hli] and a jr z, .nope inc hl inc hl cp EVOLVE_ITEM jr nz, .loop2 ``` **Fix:** ```asm .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 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 wScriptDelay, 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, [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 ``` *To do:* Fix this bug. ## `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, 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 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 [wCurPartyLevel], 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 [wCurPartyLevel], 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`. ## `CheckBugContestContestantFlag` can read beyond its data table In [engine/events/bug_contest/contest_2.asm](/engine/events/bug_contest/contest_2.asm): ```asm CheckBugContestContestantFlag: ; 139ed ; Checks the flag of the Bug Catching Contestant whose index is loaded in a. ; Bug: If a >= NUM_BUG_CONTESTANTS 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 INCLUDE "data/events/bug_contest_flags.asm" ``` However, `a < NUM_BUG_CONTESTANTS` should always be true, so in practice this is not a problem. ## `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`.