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)).
- [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)
[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`:
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):
**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.
`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.
`Pokedex_LoadAnyFootprint` in [engine/pokedex/pokedex.asm](https://github.com/pret/pokecrystal/blob/master/engine/pokedex/pokedex.asm) has to load the halves separately.
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).
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):
[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.
`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`).
`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):
**Fix:** Use `dba` instead of `dw` in `PokedexDataPointerTable`. Then edit [home.asm](https://github.com/pret/pokecrystal/blob/master/home.asm) to contain a single copy of the `PokedexDataPointerTable` lookup code, updated to work with 3-byte `dba` entries and get the bank from the first entry byte. Delete the three separate lookup routines and use the new one (placed in [home.asm](https://github.com/pret/pokecrystal/blob/master/home.asm) so it can be called from any bank.)
`BattleAnim_Cosine` and `BattleAnim_Sine` in [engine/battle_anims/functions.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle_anims/functions.asm):
`StartTrainerBattle_DrawSineWave` in [engine/battle/battle_transition.asm](https://github.com/pret/pokecrystal/blob/master/engine/battle/battle_transition.asm):
**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.
The routine `GetForestTreeFrame` in [engine/tilesets/tileset_anims.asm](https://github.com/pret/pokecrystal/blob/master/engine/tilesets/tileset_anims.asm) is hilariously inefficient.
