ref: 395ebd83866161a93276f030bbf67f6ac0895f0f
dir: /docs/design_flaws.md/
# Design Flaws These are parts of the code that do not work *incorrectly*, like [bugs and glitches](https://github.com/pret/pokecrystal/blob/master/docs/bugs_and_glitches.md), but that clearly exist just to work around a problem. In other words, with a slightly different design, the code would not need to exist at all. Design flaws may be exceptions to a usual rule, such as "tables of pointers in different banks use `dba`" ([one exception](#pic-banks-are-offset-by-pics_fix), [and another](#pokédex-entry-banks-are-derived-from-their-species-ids)) or "graphics used as a unit are stored and loaded contiguously" ([a notable exception](#footprints-are-split-into-top-and-bottom-halves)). ## Contents - [Pic banks are offset by `PICS_FIX`](#pic-banks-are-offset-by-pics_fix) - [`PokemonPicPointers` and `UnownPicPointers` are assumed to start at the same address](#pokemonpicpointers-and-unownpicpointers-are-assumed-to-start-at-the-same-address) - [Footprints are split into top and bottom halves](#footprints-are-split-into-top-and-bottom-halves) - [Music IDs $64 and $80 or above have special behavior](#music-ids-64-and-80-or-above-have-special-behavior) - [`ITEM_C3` and `ITEM_DC` break up the continuous sequence of TM items](#item_c3-and-item_dc-break-up-the-continuous-sequence-of-tm-items) - [Pokédex entry banks are derived from their species IDs](#pokédex-entry-banks-are-derived-from-their-species-ids) - [Identical sine wave code and data is repeated five times](#identical-sine-wave-code-and-data-is-repeated-five-times) - [`GetForestTreeFrame` works, but it's still bad](#getforesttreeframe-works-but-its-still-bad) ## Pic banks are offset by `PICS_FIX` [data/pokemon/pic_pointers.asm](https://github.com/pret/pokecrystal/blob/master/data/pokemon/pic_pointers.asm), [data/pokemon/unown_pic_pointers.asm](https://github.com/pret/pokecrystal/blob/master/data/pokemon/unown_pic_pointers.asm), and [data/trainers/pic_pointers.asm](https://github.com/pret/pokecrystal/blob/master/data/trainers/pic_pointers.asm) all have to use `dba_pic` instead of `dba`. This is a macro in [macros/data.asm](https://github.com/pret/pokecrystal/blob/master/macros/data.asm) that offsets banks by `PICS_FIX`: ```asm dba_pic: MACRO ; dbw bank, address db BANK(\1) - PICS_FIX dw \1 ENDM ``` The offset is translated into a correct bank by `FixPicBank` in [engine/gfx/load_pics.asm](https://github.com/pret/pokecrystal/blob/master/engine/gfx/load_pics.asm): ```asm FixPicBank: ; This is a thing for some reason. PICS_FIX EQU $36 GLOBAL PICS_FIX push hl push bc sub BANK("Pics 1") - PICS_FIX ld c, a ld b, 0 ld hl, .PicsBanks add hl, bc ld a, [hl] pop bc pop hl ret .PicsBanks: db BANK("Pics 1") ; BANK("Pics 1") + 0 db BANK("Pics 2") ; BANK("Pics 1") + 1 db BANK("Pics 3") ; BANK("Pics 1") + 2 db BANK("Pics 4") ; BANK("Pics 1") + 3 db BANK("Pics 5") ; BANK("Pics 1") + 4 db BANK("Pics 6") ; BANK("Pics 1") + 5 db BANK("Pics 7") ; BANK("Pics 1") + 6 db BANK("Pics 8") ; BANK("Pics 1") + 7 db BANK("Pics 9") ; BANK("Pics 1") + 8 db BANK("Pics 10") ; BANK("Pics 1") + 9 db BANK("Pics 11") ; BANK("Pics 1") + 10 db BANK("Pics 12") ; BANK("Pics 1") + 11 db BANK("Pics 13") ; BANK("Pics 1") + 12 db BANK("Pics 14") ; BANK("Pics 1") + 13 db BANK("Pics 15") ; BANK("Pics 1") + 14 db BANK("Pics 16") ; BANK("Pics 1") + 15 db BANK("Pics 17") ; BANK("Pics 1") + 16 db BANK("Pics 18") ; BANK("Pics 1") + 17 db BANK("Pics 19") ; BANK("Pics 1") + 18 db BANK("Pics 20") ; BANK("Pics 1") + 19 db BANK("Pics 21") ; BANK("Pics 1") + 20 db BANK("Pics 22") ; BANK("Pics 1") + 21 db BANK("Pics 23") ; BANK("Pics 1") + 22 db BANK("Pics 24") ; BANK("Pics 1") + 23 ``` **Fix:** Delete `FixPicBank` and remove all four calls to `FixPicBank` in [engine/gfx/load_pics.asm](https://github.com/pret/pokecrystal/blob/master/engine/gfx/load_pics.asm). Then use `dba` instead of `dba_pic` everywhere. ## `PokemonPicPointers` and `UnownPicPointers` are assumed to start at the same address `GetFrontpicPointer` and `GetMonBackpic` in [engine/gfx/load_pics.asm](https://github.com/pret/pokecrystal/blob/master/engine/gfx/load_pics.asm) make this assumption, which has to be accounted for in the data files. In [gfx/pics.asm](https://github.com/pret/pokecrystal/blob/master/gfx/pics.asm): ```asm ; PokemonPicPointers and UnownPicPointers are assumed to start at the same ; address, but in different banks. This is enforced in layout.link. SECTION "Pic Pointers", ROMX INCLUDE "data/pokemon/pic_pointers.asm" SECTION "Unown Pic Pointers", ROMX INCLUDE "data/pokemon/unown_pic_pointers.asm" ``` In [layout.link](https://github.com/pret/pokecrystal/blob/master/layout.link): ``` ROMX $48 org $4000 "Pic Pointers" "Pics 1" ROMX $49 org $4000 "Unown Pic Pointers" "Pics 2" ``` **Fix:** Don't enforce `org $4000` in [layout.link](https://github.com/pret/pokecrystal/blob/master/layout.link). Edit `GetFrontpicPointer`: ```diff ld a, [wCurPartySpecies] cp UNOWN jr z, .unown ld a, [wCurPartySpecies] + ld hl, PokemonPicPointers ld d, BANK(PokemonPicPointers) jr .ok .unown ld a, [wUnownLetter] + ld hl, UnownPicPointers ld d, BANK(UnownPicPointers) .ok - ld hl, PokemonPicPointers ; UnownPicPointers dec a ld bc, 6 call AddNTimes ``` And `GetMonBackpic`: ```diff - ; These are assumed to be at the same address in their respective banks. - ld hl, PokemonPicPointers ; UnownPicPointers ld a, b + ld hl, PokemonPicPointers ld d, BANK(PokemonPicPointers) cp UNOWN jr nz, .ok ld a, c + ld hl, UnownPicPointers ld d, BANK(UnownPicPointers) .ok dec a ld bc, 6 call AddNTimes ``` ## Footprints are split into top and bottom halves In [gfx/footprints.asm](https://github.com/pret/pokecrystal/blob/master/gfx/footprints.asm): ```asm ; Footprints are 2x2 tiles each, but are stored as a 16x64-tile image ; (32 rows of 8 footprints per row). ; That means there's a row of the top two tiles for eight footprints, ; then a row of the bottom two tiles for those eight footprints. ; These macros help extract the first and the last two tiles, respectively. footprint_top EQUS "0, 2 * LEN_1BPP_TILE" footprint_bottom EQUS "2 * LEN_1BPP_TILE, 2 * LEN_1BPP_TILE" ; Entries correspond to Pokémon species, two apiece, 8 tops then 8 bottoms ; 001-008 top halves INCBIN "gfx/footprints/bulbasaur.1bpp", footprint_top INCBIN "gfx/footprints/ivysaur.1bpp", footprint_top INCBIN "gfx/footprints/venusaur.1bpp", footprint_top INCBIN "gfx/footprints/charmander.1bpp", footprint_top INCBIN "gfx/footprints/charmeleon.1bpp", footprint_top INCBIN "gfx/footprints/charizard.1bpp", footprint_top INCBIN "gfx/footprints/squirtle.1bpp", footprint_top INCBIN "gfx/footprints/wartortle.1bpp", footprint_top ; 001-008 bottom halves INCBIN "gfx/footprints/bulbasaur.1bpp", footprint_bottom INCBIN "gfx/footprints/ivysaur.1bpp", footprint_bottom INCBIN "gfx/footprints/venusaur.1bpp", footprint_bottom INCBIN "gfx/footprints/charmander.1bpp", footprint_bottom INCBIN "gfx/footprints/charmeleon.1bpp", footprint_bottom INCBIN "gfx/footprints/charizard.1bpp", footprint_bottom INCBIN "gfx/footprints/squirtle.1bpp", footprint_bottom INCBIN "gfx/footprints/wartortle.1bpp", footprint_bottom ... ``` `Pokedex_LoadAnyFootprint` in [engine/pokedex/pokedex.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokedex/pokedex.asm) has to load the halves separately. **Fix:** Store footprints contiguously: ```asm INCBIN "gfx/footprints/bulbasaur.1bpp" INCBIN "gfx/footprints/ivysaur.1bpp" INCBIN "gfx/footprints/venusaur.1bpp" INCBIN "gfx/footprints/charmander.1bpp" INCBIN "gfx/footprints/charmeleon.1bpp" INCBIN "gfx/footprints/charizard.1bpp" INCBIN "gfx/footprints/squirtle.1bpp" INCBIN "gfx/footprints/wartortle.1bpp" ... ``` Edit `Pokedex_LoadAnyFootprint`: ```diff ld a, [wTempSpecies] dec a and %111 swap a ; * $10 + add a, a ld l, a ld h, 0 add hl, de ld de, Footprints add hl, de - push hl ld e, l ld d, h ld hl, vTiles2 tile $62 - lb bc, BANK(Footprints), 2 + lb bc, BANK(Footprints), 4 call Request1bpp - pop hl - - ; Whoever was editing footprints forgot to fix their - ; tile editor. Now each bottom half is 8 tiles off. - ld de, 8 tiles - add hl, de - - ld e, l - ld d, h - ld hl, vTiles2 tile $64 - lb bc, BANK(Footprints), 2 - call Request1bpp ``` ## Music IDs $64 and $80 or above have special behavior If a map's music ID in [data/maps/maps.asm](https://github.com/pret/pokecrystal/blob/master/master/data/maps/maps.asm) is $64 (the value of `MUSIC_MAHOGANY_MART` or `MUSIC_SUICUNE_BATTLE`) it will play either `MUSIC_ROCKET_HIDEOUT` or `MUSIC_CHERRYGROVE_CITY`. Moreover, if a map's music ID is $80 or above (the value of `RADIO_TOWER_MUSIC`) it might play `MUSIC_ROCKET_OVERTURE` or something else. This is caused by `GetMapMusic` in [home/map.asm](https://github.com/pret/pokecrystal/blob/master/master/home/map.asm). **Fix:** Replace `RADIO_TOWER_MUSIC | MUSIC_GOLDENROD_CITY` with `MUSIC_RADIO_TOWER` in [data/maps/maps.asm](https://github.com/pret/pokecrystal/blob/master/master/data/maps/maps.asm). Redefine the special music constants in [constants/music_constants.asm](https://github.com/pret/pokecrystal/blob/master/master/constants/music_constants.asm): ```diff -; GetMapMusic picks music for this value (see home/map.asm) -MUSIC_MAHOGANY_MART EQU $64 +; GetMapMusic picks music for these values (see home/map.asm) +MUSIC_MAHOGANY_MART EQU $fc +MUSIC_RADIO_TOWER EQU $fd ; ExitPokegearRadio_HandleMusic uses these values RESTART_MAP_MUSIC EQU $fe ENTER_MAP_MUSIC EQU $ff - -; GetMapMusic picks music for this bit flag -RADIO_TOWER_MUSIC_F EQU 7 -RADIO_TOWER_MUSIC EQU 1 << RADIO_TOWER_MUSIC_F ``` Edit `GetMapMusic`: ```diff GetMapMusic:: push hl push bc ld de, MAP_MUSIC call GetMapField ld a, c cp MUSIC_MAHOGANY_MART jr z, .mahoganymart - bit RADIO_TOWER_MUSIC_F, c - jr nz, .radiotower + cp MUSIC_RADIO_TOWER + jr z, .radiotower farcall Function8b342 ld e, c ld d, 0 .done pop bc pop hl ret .radiotower ld a, [wStatusFlags2] bit STATUSFLAGS2_ROCKETS_IN_RADIO_TOWER_F, a jr z, .clearedradiotower ld de, MUSIC_ROCKET_OVERTURE jr .done .clearedradiotower - ; the rest of the byte - ld a, c - and RADIO_TOWER_MUSIC - 1 - ld e, a - ld d, 0 + ld de, MUSIC_GOLDENROD_CITY jr .done .mahoganymart ld a, [wStatusFlags2] bit STATUSFLAGS2_ROCKETS_IN_MAHOGANY_F, a jr z, .clearedmahogany ld de, MUSIC_ROCKET_HIDEOUT jr .done .clearedmahogany ld de, MUSIC_CHERRYGROVE_CITY jr .done ``` ## `ITEM_C3` and `ITEM_DC` break up the continuous sequence of TM items [constants/item_constants.asm](https://github.com/pret/pokecrystal/blob/master/constants/item_constants.asm) defined the 50 TMs in order with `add_tm`, but `ITEM_C3` and `ITEM_DC` break up that sequence. ```asm add_tm DYNAMICPUNCH ; bf ... add_tm ROLLOUT ; c2 const ITEM_C3 ; c3 add_tm ROAR ; c4 ... add_tm DIG ; db const ITEM_DC ; dc add_tm PSYCHIC_M ; dd ... add_tm NIGHTMARE ; f2 NUM_TMS EQU const_value - TM01 - 2 ; discount ITEM_C3 and ITEM_DC ``` `GetTMHMNumber` and `GetNumberedTMHM` in [engine/items/items.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/items.asm) have to compensate for this. > There was originally a good reason for these two gaps! > > Pokémon traded from RBY to GSC have their catch rate interpreted as their new held item. This was planned early on in development, so some items were given indexes corresponding to appropriate Gen 1 catch rates: > > - $03 = 3: `BRIGHTPOWDER` is for Articuno, Zapdos, Moltres, and Mewtwo > - $1E = 30: `LUCKY_PUNCH` is for Chansey > - $23 = 35: `METAL_POWDER` is for Ditto > - $3C = 60: `SILVER_LEAF` is for 10 Pokémon > - $4B = 75: `GOLD_LEAF` is for 13 Pokémon > - $96 = 150: `MYSTERYBERRY` is for Clefairy > - $AA = 170: `POLKADOT_BOW` is for Jigglypuff > - $B4 = 180: `BRICK_PIECE` is for Machop > > Yellow was also being developed then, and it did the reverse, altering some catch rates to correspond to appropriate Gen 2 items: > > - Starter Pikachu's catch rate became 163 = $A3 for `LIGHT_BALL` > - Wild Kadabra's catch rate became 96 = $60 for `TWISTEDSPOON` > - Wild Dragonair's catch rate became 27 = $1B for `PROTEIN` > - Wild Dragonite's catch rate became 9 = $09 for `ANTIDOTE` > > Most catch rates were left as gaps in the item list, and transformed into held items via the `TimeCapsule_CatchRateItems` table in [data/items/catch_rate_items.asm](https://github.com/pret/pokecrystal/blob/master/data/items/catch_rate_items.asm). For example, the 52 Pokémon with catch rate 45 would hold the gap `ITEM_2D`, except that gets transformed into `BITTER_BERRY`. > > But a few Pokémon end up with weird items. Abra has a catch rate of 200, or $C8; and Krabby, Horsea, Goldeen, and Staryu have a catch rate of 225, or $E1. Those indexes correspond to the items `TM_PSYCH_UP` and `TM_ICE_PUNCH`, which seem like random choices—because they are. > > The TMs and HMs span from indexes $BF to $F9. However, as we can see in [pokegold-spaceworld](https://github.com/pret/pokegold-spaceworld/blob/master/constants/item_constants.asm), they *originally* spanned $C4 to $FF. For some reason they were shifted down by 5 during development. > > Before the index shift, the gap `ITEM_C3` would have been at index $C8, and `ITEM_DC` at $E1. In other words, they would have neatly corresponded to the catch rates for those five Pokémon! Then they would have held `BERRY` when traded through the Time Capsule (since the gap items get transformed via `TimeCapsule_CatchRateItems`). **Fix:** Move `ITEM_C3` and `ITEM_DC` above all the TMs in every table of item data. Edit [engine/items/items.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/items.asm): ```diff GetTMHMNumber:: ; Return the number of a TM/HM by item id c. ld a, c -; Skip any dummy items. - cp ITEM_C3 ; TM04-05 - jr c, .done - cp ITEM_DC ; TM28-29 - jr c, .skip - dec a -.skip - dec a -.done sub TM01 inc a ld c, a ret GetNumberedTMHM: ; Return the item id of a TM/HM by number c. ld a, c -; Skip any gaps. - cp ITEM_C3 - (TM01 - 1) - jr c, .done - cp ITEM_DC - (TM01 - 1) - 1 - jr c, .skip_one -.skip_two - inc a -.skip_one - inc a -.done add TM01 dec a ld c, a ret ``` ## Pokédex entry banks are derived from their species IDs `PokedexDataPointerTable` in [data/pokemon/dex_entry_pointers.asm](https://github.com/pret/pokecrystal/blob/master/data/pokemon/dex_entry_pointers.asm) is a table of `dw`, not `dba`, yet there are four banks used for Pokédex entries. The correct bank is derived from the species ID at the beginning of each Pokémon's base stats. (This is the only use the base stat species ID has.) Three separate routines do the same derivation; `GetDexEntryPointer` in [engine/pokedex/pokedex_2.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokedex/pokedex_2.asm): ```asm GetDexEntryPointer: ; return dex entry pointer b:de push hl ld hl, PokedexDataPointerTable ld a, b dec a ld d, 0 ld e, a add hl, de add hl, de ld e, [hl] inc hl ld d, [hl] push de rlca rlca maskbits NUM_DEX_ENTRY_BANKS ld hl, .PokedexEntryBanks ld d, 0 ld e, a add hl, de ld b, [hl] pop de pop hl ret .PokedexEntryBanks: db BANK("Pokedex Entries 001-064") db BANK("Pokedex Entries 065-128") db BANK("Pokedex Entries 129-192") db BANK("Pokedex Entries 193-251") ``` `GetPokedexEntryBank` in [engine/items/item_effects.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/item_effects.asm): ```asm GetPokedexEntryBank: push hl push de ld a, [wEnemyMonSpecies] rlca rlca maskbits NUM_DEX_ENTRY_BANKS ld hl, .PokedexEntryBanks ld d, 0 ld e, a add hl, de ld a, [hl] pop de pop hl ret .PokedexEntryBanks: db BANK("Pokedex Entries 001-064") db BANK("Pokedex Entries 065-128") db BANK("Pokedex Entries 129-192") db BANK("Pokedex Entries 193-251") ``` And `PokedexShow_GetDexEntryBank` in [engine/pokegear/radio.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokegear/radio.asm): ```asm PokedexShow_GetDexEntryBank: push hl push de ld a, [wCurPartySpecies] dec a rlca rlca maskbits NUM_DEX_ENTRY_BANKS ld hl, .PokedexEntryBanks ld d, 0 ld e, a add hl, de ld a, [hl] pop de pop hl ret .PokedexEntryBanks: db BANK("Pokedex Entries 001-064") db BANK("Pokedex Entries 065-128") db BANK("Pokedex Entries 129-192") db BANK("Pokedex Entries 193-251") ``` **Fix:** Use `dba` instead of `dw` in `PokedexDataPointerTable`. Delete `GetPokedexEntryBank` and `PokedexShow_GetDexEntryBank`. You can also delete `NUM_DEX_ENTRY_BANKS` from [constants/pokemon_data_constants.asm](https://github.com/pret/pokecrystal/blob/master/constants/pokemon_data_constants.asm). Edit [engine/pokedex/pokedex_2.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokedex/pokedex_2.asm): ```diff GetDexEntryPointer: ; return dex entry pointer b:de push hl ld hl, PokedexDataPointerTable ld a, b dec a ld d, 0 ld e, a add hl, de add hl, de - ld e, [hl] - inc hl - ld d, [hl] - push de - rlca - rlca - maskbits NUM_DEX_ENTRY_BANKS - ld hl, .PokedexEntryBanks - ld d, 0 - ld e, a - add hl, de - ld b, [hl] - pop de + add hl, de + ; b = bank + ld a, [hli] + ld b, a + ; de = address + ld a, [hli] + ld e, a + ld d, [hl] pop hl ret - -.PokedexEntryBanks: - db BANK("Pokedex Entries 001-064") - db BANK("Pokedex Entries 065-128") - db BANK("Pokedex Entries 129-192") - db BANK("Pokedex Entries 193-251") ``` Edit [engine/items/item_effects.asm](https://github.com/pret/pokecrystal/blob/master/engine/items/item_effects.asm): ```diff HeavyBallMultiplier: ; subtract 20 from catch rate if weight < 102.4 kg ; else add 0 to catch rate if weight < 204.8 kg ; else add 20 to catch rate if weight < 307.2 kg ; else add 30 to catch rate if weight < 409.6 kg ; else add 40 to catch rate (never happens) ld a, [wEnemyMonSpecies] ld hl, PokedexDataPointerTable dec a ld e, a ld d, 0 add hl, de add hl, de + add hl, de + ; d = bank, hl = address + ld a, BANK(PokedexDataPointerTable) + call GetFarByte + push af + inc hl ld a, BANK(PokedexDataPointerTable) call GetFarHalfword + pop de .SkipText: - call GetPokedexEntryBank + ld a, d call GetFarByte inc hl cp "@" jr nz, .SkipText - call GetPokedexEntryBank + ld a, d push bc inc hl inc hl call GetFarHalfword ``` And edit [engine/pokegear/radio.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokegear/radio.asm): ```diff PokedexShow2: ld a, [wCurPartySpecies] dec a ld hl, PokedexDataPointerTable ld c, a ld b, 0 add hl, bc add hl, bc + add hl, bc + ; b = bank + ld a, BANK(PokedexDataPointerTable) + call GetFarByte + ld b, a + inc hl + ; hl = address ld a, BANK(PokedexDataPointerTable) call GetFarHalfword - call PokedexShow_GetDexEntryBank + ld a, b push af push hl call CopyDexEntryPart1 ``` ## Identical sine wave code and data is repeated five times `_Sine` in [engine/math/sine.asm](https://github.com/pret/pokecrystal/blob/master/engine/math/sine.asm): ```asm _Sine:: ; a = d * sin(e * pi/32) ld a, e calc_sine_wave ``` `Sprites_Cosine` and `Sprites_Sine` in [engine/gfx/sprites.asm](https://github.com/pret/pokecrystal/blob/master/engine/gfx/sprites.asm): ```asm Sprites_Cosine: ; a = d * cos(a * pi/32) add %010000 ; cos(x) = sin(x + pi/2) ; fallthrough Sprites_Sine: ; a = d * sin(a * pi/32) calc_sine_wave ``` `BattleAnim_Cosine` and `BattleAnim_Sine` in [engine/battle_anims/functions.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle_anims/functions.asm): ```asm BattleAnim_Cosine: ; a = d * cos(a * pi/32) add %010000 ; cos(x) = sin(x + pi/2) ; fallthrough BattleAnim_Sine: ; a = d * sin(a * pi/32) calc_sine_wave BattleAnimSineWave ... BattleAnimSineWave: sine_table 32 ``` `StartTrainerBattle_DrawSineWave` in [engine/battle/battle_transition.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/battle_transition.asm): ```asm StartTrainerBattle_DrawSineWave: calc_sine_wave ``` And `CelebiEvent_Cosine` in [engine/events/celebi.asm](https://github.com/pret/pokecrystal/blob/master/engine/events/celebi.asm): ```asm CelebiEvent_Cosine: ; a = d * cos(a * pi/32) add %010000 ; cos(x) = sin(x + pi/2) calc_sine_wave ``` They all rely on `calc_sine_wave` in [macros/code.asm](https://github.com/pret/pokecrystal/blob/master/macros/code.asm): ```asm calc_sine_wave: MACRO ; input: a = a signed 6-bit value ; output: a = d * sin(a * pi/32) and %111111 cp %100000 jr nc, .negative\@ call .apply\@ ld a, h ret .negative\@ and %011111 call .apply\@ ld a, h xor $ff inc a ret .apply\@ ld e, a ld a, d ld d, 0 if _NARG == 1 ld hl, \1 else ld hl, .sinetable\@ endc add hl, de add hl, de ld e, [hl] inc hl ld d, [hl] ld hl, 0 .multiply\@ ; factor amplitude srl a jr nc, .even\@ add hl, de .even\@ sla e rl d and a jr nz, .multiply\@ ret if _NARG == 0 .sinetable\@ sine_table 32 endc ENDM ``` And on `sine_table` in [macros/data.asm](https://github.com/pret/pokecrystal/blob/master/macros/data.asm): ```asm sine_table: MACRO ; \1 samples of sin(x) from x=0 to x<32768 (pi radians) x = 0 rept \1 dw (sin(x) + (sin(x) & $ff)) >> 8 ; round up x = x + DIV(32768, \1) ; a circle has 65536 "degrees" endr ENDM ``` **Fix:** Edit [home/sine.asm](https://github.com/pret/pokecrystal/blob/master/home/sine.asm) to contain a single copy of the (co)sine code in bank 0, and call it from those five sites. ## `GetForestTreeFrame` works, but it's still bad The routine `GetForestTreeFrame` in [engine/tilesets/tileset_anims.asm](https://github.com/pret/pokecrystal/blob/master/engine/tilesets/tileset_anims.asm) is hilariously inefficient. **Fix:** Edit `GetForestTreeFrame`: ```diff GetForestTreeFrame: ; Return 0 if a is even, or 2 if odd. - and a - jr z, .even - cp 1 - jr z, .odd - cp 2 - jr z, .even - cp 3 - jr z, .odd - cp 4 - jr z, .even - cp 5 - jr z, .odd - cp 6 - jr z, .even -.odd - ld a, 2 - scf - ret -.even - xor a + and 1 + add a ret ```