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Game

Pokémon Emerald

A Generation III Pokémon game for Game Boy Advance, read through the pret/pokeemerald decompilation.

draftAlso: Pokémon Emerald VersionUpdated 2026-10-20
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Pokémon Emerald is a Generation III Game Boy Advance game, released in Japan in September 2004 and North America in May 20051. The code read here is pret’s pokeemerald decompilation, C that compiles to the original ROM.

Its type effectiveness table is Pokémon Crystal‘s, row for row2. Effectiveness text now comes from flags, where a ½ row and a 2× row cancel3. Levitate acts before the rows, and Wonder Guard after4,5.

Uses

Linked from

Every claim about this game, by concept (16)
generalPokémon Emerald (developer Game Freak, publisher Nintendo, Game Boy Advance, and Generation III core series) came out in Japan on 16 September 2004 and North America on 1 May 2005.T1
Damage formulaType still decides physical or special in Emerald, by its position relative to TYPE_MYSTERY.T3
A plain damaging move runs critcalc, damagecalc (base damage), typecalc (STAB, then type rows), and then adjustnormaldamage (random factor).T3
The random factor changes form: damage × (100 − rand % 16) / 100, i.e. 85–100 %, raised to 1 if that gives 0.T3
Same-type attack bonusBefore the type chart, Cmd_typecalc applies STAB as damage×15/10 when either attacker type equals the move's type.T3
Type effectivenessEmerald's type chart, gTypeEffectiveness, is a flat u8 array of 108 non-neutral (attacker, defender, multiplier) rows over 17 types, then a TYPE_FORESIGHT marker, two Ghost immunities, and TYPE_ENDTABLE.T3
Emerald keeps the Game Boy encoding, now named TYPE_MUL_*: 20 super effective, 10 normal, 5 not effective, and 0 no effect.T3
Emerald's table holds the same 110 rows as Crystal's, in the same order: no new type and no changed matchup.T4
TYPE_MYSTERY (9), named "???", sits between the physical and special types and has no rows.T3
For each row of the move's type, ModulateDmgByType runs once per distinct target type it matches: damage×multiplier/10, raised from 0 to 1 unless the multiplier is 0.T3
The text comes from flags ModulateDmgByType sets per row: a 2× row cancels an earlier not-very-effective flag, a ½ row an earlier super-effective one, and ×0 sets "doesn't affect", clearing both.T3
Against a Foresight target, the loop breaks at the TYPE_FORESIGHT row, skipping the Normal→Ghost and Fighting→Ghost immunities after it.T3
Struggle skips Cmd_typecalc entirely, so neither STAB nor the type chart touches it.T3
Cmd_typecalc flags a Ground move against a Levitate target as missed and “doesn't affect”, and walks no type row.T3
After the rows, a Wonder Guard target makes a damaging move miss on the turn it attacks, unless the move carries the super-effective flag without the not-very-effective one.T3
Row order still matters: an Ice move against Water/Flying takes 3 damage to 1, then 2 (½ row at L369, 2× at L373).T4

References

  1. ^Pokémon Emerald (developer Game Freak, publisher Nintendo, Game Boy Advance, and Generation III core series) came out in Japan on 16 September 2004 and North America on 1 May 2005. T1Bulbapedia, “Pokémon Emerald Version” · infobox, Basic info and Release dates
  2. ^Emerald's table holds the same 110 rows as Crystal's, in the same order: no new type and no changed matchup. T4pret/pokecrystal · data/types/type_matchups.asm L1–118pret/pokeemerald · src/battle_main.c L335–449Bulbapedia, “Type/Type chart” · Type charts: Generations II-Vprobe probes/pokemon-types/type-charts.mjs
  3. ^The text comes from flags ModulateDmgByType sets per row: a 2× row cancels an earlier not-very-effective flag, a ½ row an earlier super-effective one, and ×0 sets "doesn't affect", clearing both. T3pret/pokeemerald · src/battle_script_commands.c L1327–1352
  4. ^Cmd_typecalc flags a Ground move against a Levitate target as missed and “doesn't affect”, and walks no type row. T3pret/pokeemerald · src/battle_script_commands.c L1375–1384
  5. ^After the rows, a Wonder Guard target makes a damaging move miss on the turn it attacks, unless the move carries the super-effective flag without the not-very-effective one. T3pret/pokeemerald · src/battle_script_commands.c L1409–1419

Sources

Code

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