This tutorial is for how to add a new type for Pokémon or moves. As an example, we'll add the Fairy type introduced in Gen 6.


## Contents

1. [Define a type constant](#1-define-a-type-constant)
2. [Give the type a name](#2-give-the-type-a-name)
3. [List the type matchups](#3-list-the-type-matchups)
4. [Make it searchable in the Pokédex](#4-make-it-searchable-in-the-pokédex)
5. [Update Pokémon types](#5-update-pokémon-types)
6. [Update move types](#6-update-move-types)
7. [Change Polkadot Bow to boost Fairy moves](#7-change-polkadot-bow-to-boost-fairy-moves)


## 1. Define a type constant

Gen 2 was before the physical/special split, so the types after `SPECIAL` count as special, and the rest count as physical. Fairy moves are mostly special, so we'll add it there.

Edit [constants/type_constants.asm](../blob/master/constants/type_constants.asm):

```diff
 SPECIAL EQU const_value
 	const FIRE
 	const WATER
 	const GRASS
 	const ELECTRIC
 	const PSYCHIC_TYPE
 	const ICE
 	const DRAGON
 	const DARK
+	const FAIRY
 TYPES_END EQU const_value
```

(If you're using an old version of pokecrystal where the `EGG_FAIRY` egg group constant was still called `FAIRY`, you'll have to name the type something different, like `FAIRY_TYPE` or `FAERIE`.)


## 2. Give the type a name

Edit [data/types/names.asm](../blob/master/data/types/names.asm):

```diff
 TypeNames:
 ; entries correspond to types (see constants/type_constants.asm)
 	dw Normal
 	...
 	dw Dark
+	dw Fairy

 Normal:    db "NORMAL@"
 ...
 Dark:      db "DARK@"
+Fairy:     db "FAIRY@"
```


## 3. List the type matchups

Edit [data/types/type_matchups.asm](../blob/master/data/types/type_matchups.asm):

```diff
 TypeMatchups:
 	;  attacker,  defender,  *=
 	db NORMAL,    ROCK,      NOT_VERY_EFFECTIVE
 	db NORMAL,    STEEL,     NOT_VERY_EFFECTIVE
 	...
 	db FIGHTING,  STEEL,     SUPER_EFFECTIVE
+	db FIGHTING,  FAIRY,     NOT_VERY_EFFECTIVE
 	...
 	db POISON,    STEEL,     NO_EFFECT
+	db POISON,    FAIRY,     SUPER_EFFECTIVE
 	...
 	db BUG,       STEEL,     NOT_VERY_EFFECTIVE
+	db BUG,       FAIRY,     NOT_VERY_EFFECTIVE
 	...
 	db DRAGON,    STEEL,     NOT_VERY_EFFECTIVE
+	db DRAGON,    FAIRY,     NO_EFFECT
 	...
 	db DARK,      STEEL,     NOT_VERY_EFFECTIVE
+	db DARK,      FAIRY,     NOT_VERY_EFFECTIVE
 	...
 	db STEEL,     STEEL,     NOT_VERY_EFFECTIVE
+	db STEEL,     FAIRY,     SUPER_EFFECTIVE
+	db FAIRY,     FIRE,      NOT_VERY_EFFECTIVE
+	db FAIRY,     FIGHTING,  SUPER_EFFECTIVE
+	db FAIRY,     POISON,    NOT_VERY_EFFECTIVE
+	db FAIRY,     DRAGON,    SUPER_EFFECTIVE
+	db FAIRY,     DARK,      SUPER_EFFECTIVE
+	db FAIRY,     STEEL,     NOT_VERY_EFFECTIVE

 	db -2 ; end (with Foresight)

 ; Foresight removes Ghost's immunities.
 	db NORMAL,    GHOST,     NO_EFFECT
 	db FIGHTING,  GHOST,     NO_EFFECT

 	db -1 ; end
```


## 4. Make it searchable in the Pokédex

These tables are used for the Pokédex's type search feature.

Edit [data/types/search_types.asm](../blob/master/data/types/search_types.asm):

```diff
 PokedexTypeSearchConversionTable:
 ; entries correspond with PokedexTypeSearchStrings (see data/types/search_strings.asm)
 	db NORMAL
 	...
 	db STEEL
+	db FAIRY
```

Edit [data/types/search_strings.asm](../blob/master/data/types/search_strings.asm):

```diff
 PokedexTypeSearchStrings:
 ; entries correspond with PokedexTypeSearchConversionTable (see data/types/search_types.asm)
 	db "  ----  @"
 	db " NORMAL @"
 	...
 	db " STEEL  @"
+	db " FAIRY  @"
```


## 5. Update Pokémon types

Edit the type entries in [data/pokemon/base_stats/](../blob/master/data/pokemon/base_stats/):

- [azumarill.asm](../blob/master/data/pokemon/base_stats/azumarill.asm): `WATER, WATER` → `WATER, FAIRY`
- [clefable.asm](../blob/master/data/pokemon/base_stats/clefable.asm): `NORMAL, NORMAL` → `FAIRY, FAIRY`
- [clefairy.asm](../blob/master/data/pokemon/base_stats/clefairy.asm): `NORMAL, NORMAL` → `FAIRY, FAIRY`
- [cleffa.asm](../blob/master/data/pokemon/base_stats/cleffa.asm): `NORMAL, NORMAL` → `FAIRY, FAIRY`
- [granbull.asm](../blob/master/data/pokemon/base_stats/granbull.asm): `NORMAL, NORMAL` → `FAIRY, FAIRY`
- [igglybuff.asm](../blob/master/data/pokemon/base_stats/igglybuff.asm): `NORMAL, NORMAL` → `NORMAL, FAIRY`
- [jigglypuff.asm](../blob/master/data/pokemon/base_stats/jigglypuff.asm): `NORMAL, NORMAL` → `NORMAL, FAIRY`
- [marill.asm](../blob/master/data/pokemon/base_stats/marill.asm): `WATER, WATER` → `WATER, FAIRY`
- [mr__mime.asm](../blob/master/data/pokemon/base_stats/mr__mime.asm): `PSYCHIC_TYPE, PSYCHIC_TYPE` → `PSYCHIC_TYPE, FAIRY`
- [snubbull.asm](../blob/master/data/pokemon/base_stats/snubbull.asm): `NORMAL, NORMAL` → `FAIRY, FAIRY`
- [togepi.asm](../blob/master/data/pokemon/base_stats/togepi.asm): `NORMAL, NORMAL` → `FAIRY, FAIRY`
- [togetic.asm](../blob/master/data/pokemon/base_stats/togetic.asm): `NORMAL, FLYING` → `FAIRY, FLYING`
- [wigglytuff.asm](../blob/master/data/pokemon/base_stats/wigglytuff.asm): `NORMAL, NORMAL` → `NORMAL, FAIRY`


## 6. Update move types

Edit the type columns in [data/moves/moves.asm](../blob/master/data/moves/moves.asm):

- `CHARM`: `NORMAL` → `FAIRY`
- `SWEET_KISS`: `NORMAL` → `FAIRY`
- `MOONLIGHT`: `NORMAL` → `FAIRY`


## 7. Change Polkadot Bow to boost Fairy moves

At this point we're technically done: all the canon aspects of the Fairy type are implemented. (If you want to add new Fairy-type Pokémon or moves, check out different tutorials.) But there's no held type-boosting item for it, and Gen 2 happens to have the unavailable `POLKADOT_BOW` item that boosts Normal moves like `PINK_BOW`, so let's change it to boost Fairy moves instead.

Edit [constants/item_data_constants.asm](../blob/master/constants/item_data_constants.asm):

```diff
 const_value set 50
 	const HELD_NORMAL_BOOST
 	...
 	const HELD_STEEL_BOOST
+	const HELD_FAIRY_BOOST
```

Edit [data/types/type_boost_items.asm](../blob/master/data/types/type_boost_items.asm):

```diff
 TypeBoostItems:
-	db HELD_NORMAL_BOOST,   NORMAL   ; PINK_BOW/POLKADOT_BOW
+	db HELD_NORMAL_BOOST,   NORMAL   ; PINK_BOW
 	...
 	db HELD_STEEL_BOOST,    STEEL    ; METAL_COAT
+	db HELD_FAIRY_BOOST,    FAIRY    ; POLKADOT_BOW
 	db -1
```

Edit [data/items/attributes.asm](../blob/master/data/items/attributes.asm):

```diff
 ItemAttributes:
 ; entries correspond to constants/item_constants.asm
 ...
 ; POLKADOT_BOW
-	item_attribute 100, HELD_NORMAL_BOOST, 10, CANT_SELECT, ITEM, ITEMMENU_NOUSE, ITEMMENU_NOUSE
+	item_attribute 100, HELD_FAIRY_BOOST, 10, CANT_SELECT, ITEM, ITEMMENU_NOUSE, ITEMMENU_NOUSE
```

And lastly, edit [data/items/descriptions.asm](../blob/master/data/items/descriptions.asm):

```diff
 PolkadotBowDesc:
-	db   "Powers up normal-"
+	db   "Powers up fairy-"
 	next "type moves. (HOLD)@"
```

*Now* we're done!

![Screenshot](screenshots/fairy-type.png)

If you're just varying the original Crystal game, note that you can get three Pink Bows (one from Tuscany on Tuesdays, one from Mary after clearing Team Rocket from Radio Tower, and one from Picnicker Tiffany if you get her phone number), so one of those can be replaced with a Fairy-boosting Polkadot Bow.

You'll also need damaging Fairy moves like Moonblast and Dazzling Gleam, so look up how to add those in the new move tutorial.