Crystal/docs/NATIVE_PORT.md

# Native port status and reference checks

## Reproducible reference

The private `.reference/pokecrystal` checkout is pinned to `7a7881d0d62e0ddbd82dcf10e7116807487ac651`. With RGBDS 1.0.3, its `crystal11` build is byte-identical to the supplied English US/Europe revision 1.1 ROM. `npm run check:reference` verifies the files and commit. It checks every ROM and RAM address in `src/game/rom/profile.ts` against generated symbols, event constants against `constants/event_flags.asm`, and map-group bounds against `data/maps/maps.asm`.

To recreate the private reference:

```sh
git clone https://github.com/pret/pokecrystal.git .reference/pokecrystal
git -C .reference/pokecrystal checkout 7a7881d0d62e0ddbd82dcf10e7116807487ac651
make -C .reference/pokecrystal crystal11 -j4
npm run check:reference
```

Install RGBDS 1.0.3 separately. No script downloads a game ROM. `CRYSTAL_ROM_PATH` optionally selects another local location; checks otherwise use `Pokemon - Crystal Version (UE) (V1.1) [C][!].gbc` at the root.

The reference checkout, rebuilt ROM, extracted graphics, saves and gameplay screenshots must stay local and ignored. The shipping profile contains addresses and format constants, not game content.

## Routine map

These paths refer to the pinned [PRET source](https://github.com/pret/pokecrystal/tree/7a7881d0d62e0ddbd82dcf10e7116807487ac651).

| Native module                    | PRET reference                                                                                                                 | Evidence and limits                                                                                                                                                                                                                     |
| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `game/rom/lz.ts`                 | `home/decompress.asm`                                                                                                          | All LZ command types have unit vectors; six tilesets match original ASM execution byte-for-byte.                                                                                                                                        |
| `game/rom/assets.ts` maps/events | `data/maps/maps.asm`, `data/maps/attributes.asm`, `data/maps/scenes.asm`, `data/maps/landmarks.asm`, `macros/scripts/maps.asm` | Any map header in the ROM's 26 groups decodes; only maps explicitly listed in NATIVE_MAPS can be entered. Location names, scene-variable owners and connection offsets come from the ROM.                                                                 |
| Tiles/palettes                   | `home/map.asm`, `engine/gfx/color.asm`, `engine/tilesets/mapgroup_roofs.asm`                                                   | Graphics match rebuilt reference bytes. Connected maps draw beyond the edges with the current tileset, like the original strips. Native tileset animation and special palettes; Johto, Ice Path, restless Ilex Forest and Tin Tower each match 96 reference VRAM frames. 192 palette cases match the original routine.                                                  |
| Sprites/rendering                | `data/sprites/sprites.asm`, `data/sprites/facings.asm`, `data/sprites/emotes.asm`                                              | Chris/Kris, standard NPCs, emote bubbles and jump shadows decoded. Walking frames follow `SetFacingStepAction`. Variable sprites and Pokémon icons decoded; grass priority supported. Owned room decorations support selection, removal, slot placement, descriptions and validated saves.                                                                     |
| `game/world/world.ts`            | `engine/overworld/events.asm`, `player_movement.asm`, `warp_connection.asm`, `data/collision/collision_permissions.asm`        | 30 Hz overworld ticks, 8-tick walks, 16-tick ledge jumps, directional mats, animated door/stair exits, connection coordinates, events, scenes and callbacks. NPC random walks and spins follow `HandleNPCStep`. Forced movement, Surf, Cut, Strength, cycling rules, pits and elevators implemented. Fourteen reference traces compare turn timing, actors and event flags; map-entry boundaries verify the completed destination. Bicycle access uses the Key Items menu. |
| Event interpreter                | `macros/scripts/events.asm`, `engine/overworld/scripting.asm`, `engine/events/std_scripts.asm`                                 | Resumable; yields text, choices, movement, emotes and pauses. Scenes, phone contacts, string buffers and object commands. Unknown commands and specials abort without committing.                                                       |
| Movement interpreter             | `macros/scripts/movement.asm`, `engine/overworld/movement.asm`, `engine/overworld/map_objects.asm`                             | Turns, steps, slides, jumps (two tiles with the original arc), sleeps, facing locks, visibility and emotes. `follow` takes one tile toward the leader's previous square. All movement opcodes decode, including teleport, fishing, skyfall, shake and flicker poses; Controlled reference scenes check spin, teleport, skyfall, fishing and flicker direction, visibility and lift.                                                              |
| Specials                         | `data/events/special_pointers.asm`, `engine/rtc/timeset.asm`, `engine/overworld/decorations.asm`                               | Selected by routine address from the ROM table: `SetDayOfWeek`, initial DST flags, `RestartMapMusic` (no audio yet), room decoration toggles, `PokemonCenterPC` and `PlayersHousePC` (Bill's, the player's and Oak's PCs), the Town Map, `HealParty`, `HealMachineAnim` (presentation only), `CheckPokerus` and the `StubbedTrainerRankings_Healings` stub.                                                                              |
| `game/scripts/pc.ts`             | `engine/events/pokecenter_pc.asm`, `engine/pokemon/bills_pc_top.asm`, `engine/pokemon/bills_pc.asm`, `engine/events/prof_oaks_pc.asm`, `engine/events/std_collision.asm` | The Pokémon Center and house PCs: Bill's PC (deposit, withdraw, release, change and name boxes), item storage, the empty mail box and Oak's rating. Menu strings and texts come from the ROM; lists are native. Moving Pokémon, the stats screen and printing are not ported. |
| `game/rom/pokemon.ts`            | `data/pokemon/base_stats`, `evos_attacks.asm`, `data/moves/moves.asm`, `data/items/attributes.asm`, `engine/gfx/load_pics.asm` | Species, move and item names, base data, evolution lists, learnsets, move PP, item pockets, growth-rate exp and front pictures (`FixPicBank`, `PadFrontpic`). Starter pictures match rebuilt bytes; all 251 evolution lists match the pinned source. |
| `game/party`                     | `engine/pokemon/move_mon.asm`, `engine/pokemon/caught_data.asm`, `engine/items/items.asm`                                      | `GeneratePartyMonStats` for script gifts: DVs, `FillMoves`, PP, exp, `CalcMonStatC`, happiness and caught data. `PutItemInPocket`, key items and `TossItem`. `SendMonIntoBox`, `SendGetMonIntoFromBox` (deposit and withdraw), `RestorePPOfDepositedPokemon` and `CalcLevel` for the PC's boxes and item storage. TMs and HMs are refused.                                         |
| Text interpreter                 | `macros/scripts/text.asm`, `constants/charmap.asm`, `home/text.asm`                                                            | Literal/far text, RAM names and string buffers from native state, numbers of dots, and sound or pause cues (consumed). `text_asm` and other RAM reads are refused.                                                                      |

Supported event opcodes are explicit in the interpreter switch. Audio commands consume their operands, but sound sequencing is pending; those opcodes do not imply complete audiovisual behavior. `pause` holds the current text or waits the original number of overworld ticks.

Scripts run on a private draft. The world presents each yielded effect, then resumes the script with the player's answer or when the animation ends. The draft is committed only when the script ends. A save made during a scene returns the committed state, and coordinate events rewind to the source of the triggering walk or two-tile jump. Saves during movement also retain the source tile until arrival events run, including across map connections. A failed scene restores the positions it had changed. As in `LoadMapObjects`, map objects spawn when the map loads. Later flag changes do not remove objects already shown; only `appear` and `disappear` do.

The opening scenes currently run end to end from the ROM: Mom's Pokégear, weekday and DST scene, the teacher at the west edge, the rival at the lab window, Elm's introduction with its yes/no loop, the lab's exit guard, the starter choice with `pokepic`, `givepoke` and the nickname prompt, Elm's directions and the aide's Potion through the ROM's own `GiveItemScript`. `callasm` accepts only explicitly empty routines or native translations: `HalveMoney`, `GetWhiteoutSpawn`, the item ball's `TryReceiveItem` and the fruit tree routines. The naming screen is a native text field limited to the characters the original offers.

## Actual emulator comparison

`tests/reference-parity.spec.ts` loads the user's ROM into the reference emulator and places a small original test trampoline in emulated WRAM. It calls the ROM's `FarDecompress` routine at `$0b40`, then sets a return sentinel. Every output byte is compared with the native decoder for six supported map tilesets. This executes the original routine rather than comparing two copies of our code.

The same suite compares 400 damage cases and 400 type-effectiveness cases per browser against the original battle routines, 300 `CalcMonStats` cases (with and without stat experience, including levels above 100 that reach the 999 cap) and every `CalcExpAtLevel` value for the six growth rates and levels 1–100. Battle unit tests cover win, escape, loss, experience, level-up and move-learning flows, and `tests/playthrough.test.ts` plays the whole opening quest from a new game through `GameWorld`'s inputs, with save/reload after each stage. This establishes parity only for the compared routines and inputs. It does not prove complete gameplay, rendering, battles, audio, timing or physical-device parity. Extend controlled comparisons as each subsystem is translated.

## Validation

```sh
npm test
npm run test:e2e
npm run check:reference
npm run check:vendor
npm run build
npm run check:release
npm run build:reference
```

User-ROM tests skip when the file is absent, including public CI. Synthetic tests still run. Comparing with rebuilt graphics also needs the private PRET build. Do not report skipped private checks as CI passes.

Native production is `dist/`; the optional reference output is `dist-reference/`. Release checks reject emulator dependencies, binary game files and embedded binary assets in the native output. Source review is still required when adding assets or data.

## Save schema

Native saves are version 3. Version 2 added scene values by owning map, phone contacts, the weekday offset and DST flag, and positions of objects that scripts moved on the current map. Version 3 adds the player ID, party, bag, Pokédex seen/caught sets and money. Early version-3 backups without money receive the original starting balance; explicitly invalid balances are rejected. Restores recompute each Pokémon's stats from its DVs and reject any mismatch, and check every item against its ROM pocket. Older saves migrate with new-game defaults; a missing player ID is drawn as a new game draws it. Objects are restored from the save on continue, and only the TILES callback runs, as in `MapSetupScript_Continue`.

## Scripted trainer battle foundation

`game/rom/trainers.ts` decodes `TrainerGroups`, `TrainerClassAttributes`, `TrainerClassNames`, `TrainerClassDVs` and map trainer headers. Tests cover all 542 ROM records across 67 classes; CAL2 construction refuses its SRAM-dependent Mystery Gift party.

`game/battle/ai.ts` translates `AIChooseMove`, `AI_Redundant` and the Basic, Setup, Types, Offensive, Opportunist, Aggressive, Cautious, Status and Risky layers. It preserves the original random tie selection, known redundancy quirks, HP thresholds, exclusions and the deterministic pre-variation damage estimate used by Aggressive and Risky. Smart runs only for move effects that have no `AI_Smart_EffectHandlers` entry (Normal Hit, Attack Down, Defense Down; enough for the first rival). Other effects are refused before any random draw. Synthetic scoring vectors establish the tested branches; original-engine AI execution parity is still pending.

`loadtrainer`, `winlosstext` and `startbattle` run scripted trainer battles through the existing battle UI. Tests cover Joey's ROM party/text/reward, RUN refusal, trainer experience, Amulet Coin, CANLOSE behavior, money limits, transactional rollback and midbattle restore. Chromium and WebKit exercise the UI with a test-only script.

## Map trainers

`home/trainers.asm` and `engine/events/trainer_scripts.asm`: talking to an `OBJECTTYPE_TRAINER` object runs `TalkToTrainerScript` with the object's header copied as `wTempTrainer`; `_CheckTrainerBattle` runs `SeenByTrainerScript` with `wSeenTrainerDistance`. The world checks sight in `PlayerEvents` order: before warps, coordinate events and encounters at the end of a step (a seen player's tile events are then skipped, as `DisableEvents` does), and on idle ticks before scene scripts and input. Walls and objects do not block sight. `TrainerWalkToPlayer`/`ComputePathToWalkToPlayer` build the raw `wMovementBuffer` bytes, which `applymovementlasttalked` decodes with the normal movement reader. `wRunningTrainerBattleScript` lives in the script run: zero at the start, set by `loadmem` after the battle so `endifjustbattled` ends the after-script. Trainer commands without a map trainer are refused. `MomTriesToBuySomething` after scripted battles does nothing while Mom's savings (not ported) are zero.

`engine/battle/core.asm` and `engine/battle/ai/items.asm`, `switch.asm`: when a trainer's Pokémon faints and others remain, `UpdateBattleStateAndExperienceAfterEnemyFaint` zeroes its party HP and runs `NewEnemyMonStatus`; `EnemyPartyMonEntrance` then sends out the Pokémon chosen by `FindMonInOTPartyToSwitchIntoBattle`. When every candidate is threatened it draws `BattleRandom & 7`, which tests pin. `AI_SwitchOrTryItem` runs before either side moves: `CheckAbleToSwitch`, the Often/Rarely/Sometimes thresholds, `AI_TrySwitch` and `AI_Switch` (withdraw text, HP and status back to the party). `CheckTypeMatchup` ignores the type its switch-AI callers load and uses `BATTLE_VARS_MOVE_TYPE`, so every such matchup uses the enemy's chosen move type; `FindEnemyMonsWithASuperEffectiveMove` never resets its result between Pokémon; `FindEnemyMonsWithAtLeastQuarterMaxHP` rotates HP bits instead of multiplying. All three bugs are kept. `UsedMoveText` records `wPlayerUsedMoves`. Refused: Pursuit on a switching Pokémon, Perish Song, Spikes, and trainer items. Side effects of the type scans on the move structs (overwritten types and animation) are not modelled; the next `ParseEnemyAction`/`ParsePlayerAction` reloads them.

`BGEVENT_ITEM` runs `HiddenItemScript` with `wHiddenItemData`; `SetMemEvent` sets the item's flag.

A trainer sighting whose script is refused is not restarted until the player moves. This is a native safeguard, not original behavior.

## Next slice

Route 29, Cherrygrove, Route 30 and Mr. Pokémon's house are enabled with item balls, hidden items, fruit trees and the daily reset, the Pokémon Center nurse, the recorded whiteout spawn, map trainers, the first rival battle, Elm's special call, capture and the catching tutorial. NPCs roam. The PC and boxes are ported. Next: party, bag and Pokégear menus over the native models. Other specials stay refused until translated.

## Reflect and Light Screen

`BattleCommand_Screen` in `engine/battle/effect_commands.asm` and `HandleScreens`
in `engine/battle/core.asm` now run natively. Each screen has a side-owned
five-turn counter, including its setup turn. Repeated use fails without
refreshing it; send-outs preserve it. Expiration runs after defrost, before
healing items, player before enemy and Light Screen before Reflect. Messages
come from the ROM. The existing damage path doubles the appropriate defense
and retains the original critical/stage rule. Safeguard and other screen
flags remain refused. Seven local-ROM tests cover move execution, counters,
PP, damage stats and send-out persistence; no screen-routine emulator parity
or physical-device validation is claimed.

## Mr. Pokémon, the first rival and special calls

`MrPokemonsHouse.asm`, `CherrygroveRivalScene*` and the `ElmsLab.asm` officer
and Egg scripts run from the ROM. Supporting translations: `blackoutmod`,
`reloadmap` (returns to the script; native presentation keeps the map),
`readvar VAR_SPECIALPHONECALL` and `memcall` (only through
`wCallerContact + PHONE_CONTACT_SCRIPT2_BANK`). Specials: `NameRival` (native
naming field, ROM title and `InitName` default), `FadeOutMusic`, and the
presentation-only fades. `CountStep`'s `CheckSpecialPhoneCall` reads the
queued `SpecialPhoneCallList` entry. It checks `SpecialCallOnlyWhenOutside`
or `SpecialCallWhereverYouAre`, then runs `CheckSpecialPhoneCall.script` with
that entry's caller script. `RingTwice_StartCall` and `InitCallReceiveDelay`
are accepted without effect, because ringing presentation and random calls are
not ported. `HangUp` shows "Click!" for its 140 frames. Local-ROM tests cover
the house, both rival triggers with all three parties, a rival loss, the call
indoors, outdoors and on reload, the officer's naming (including blank names
and reload at the naming screen), and the Egg and Poké Ball handovers. Browser
tests cover the house, the rival battle and the naming field.

## Capture and the catching tutorial

`PokeBallEffect`, `BallMultiplierFunctionTable` (Poké, Great, Ultra and
Master Balls), `GetPokeBallWobble` with `WobbleProbabilities`,
`UseBallInTrainerBattle` and `BattleMenu_Pack`'s `.UseItem` in
`engine/items/item_effects.asm`, `engine/battle_anims/pokeball_wobble.asm`
and `engine/battle/core.asm`. The catch rate is computed with the original
8- and 16-bit arithmetic and kept bugs (no bonus for BRN/PSN/PAR, overflow
above 341 maximum HP). Only the random draws are kept from the throw
animation: one per shake until the ball clicks or the Pokémon breaks free.
The caught Pokémon follows the second `LoadEnemyMon` (the wild item roll
is redrawn and then restored), `GeneratePartyMonStats` with `wBattleMode`
set (wild moves, PP and HP) and `SetCaughtData`. Pokédex registration,
`NewDexDataText`, `AskGiveNicknameText` and the naming field with
`InitName`'s default follow. The ball is taken from the selected slot, as
`RemoveItemFromPocket` does with `wCurItemQuantity`.

`Script_catchtutorial` and `CatchTutorial` run the battle as
`BATTLETYPE_TUTORIAL`: `<PLAYER>` reads "DUDE" from the ROM, `DoBattle`
skips the send-out, and the auto input's PACK and ball choice go straight
to `PokeBallEffect`, which always catches and keeps nothing (`.FinishTutorial`).
Prompts continue on their own. The Dude's back picture, the ball animation,
capture music and the Pokédex page (`NewPokedexEntry`) are not presented.
`TX_LOW` text is now read as a line break.

Refused: the other ball
multipliers, Park/Safari Balls, a transformed target and a catch-rate
division by zero. Pure vectors cover the catch formula; local-ROM tests
cover capture, every break-free message, Master Ball draws, blank
nicknames, the blocked trainer ball, full-party rollback, both tutorial
triggers, declining and the repeat offer, and mid-battle reloads. Browser
tests cover PACK, catching and naming. No emulator comparison of the
capture routines has been run.

## Switching and healing items in battle

`engine/battle/core.asm`: `BattleMenu_PKMN` and `TryPlayerSwitch` ("is
already out", "can't be recalled" while wrapped or blocked by Mean Look,
`CheckIfCurPartyMonIsFitToFight` with its fainted and Egg texts),
`PlayerSwitch` and `BattleMonEntrance`. The switch runs `ParseEnemyAction`
first, and `ParsePlayerAction` then skips it, so the random draws happen
once. `SendOutMonText` and `WithdrawMonText` choose their cheer from the
enemy's HP as a byte percentage of max HP / 4, including
`wEnemyHPAtTimeOfPlayerSwitch`. A maximum HP below 4 would divide by zero
and freeze the original; it is refused. `PursuitSwitch` reads the enemy
move's effect as `GetMoveEffect` does, and Pursuit is refused.

After a faint, `HandlePlayerMonFaint` runs `AskUseNextPokemon` (wild
battles only; NO tries to run, compared with the first party Pokémon's
stored Speed) and `ForcePlayerMonChoice`, whose party menu cannot be
cancelled. A double faint in a trainer battle goes through `DoubleSwitch`,
and a fainted Pokémon gains no share of the experience. When a trainer
sends out the next Pokémon, `CheckWhetherToAskSwitch` and `OfferSwitch` run
Shift mode's offer (the only battle style, since options are not ported);
switching clears both participant sets as the original does.
`NewBattleMonStatus` also clears the enemy's wrap count and Mean Look.

`engine/items/item_effects.asm` and `pack.asm`: `BattlePack` shows the Items
and Balls pockets. `CheckItemContext` gives Oak's "This isn't the time"
text for items with no battle use. `ItemEffects` is read from the ROM:
`RestoreHPEffect` (`ItemRestoreHP`, `HealingHPAmounts`, `RestoreHealth`) and
`StatusHealingEffect` (`UseStatusHealer`, `StatusHealingActions`,
`HealStatus`, `IsItemUsedOnConfusedMon`) run with `UseItem_SelectMon`, the
party menu action texts and `UseDisposableItem`. "Won't have any effect"
and a cancelled menu keep the item and the turn. `wItemEffectSucceeded`
shares `wBattlePlayerAction`'s byte, so a used item takes the turn.
`CalcPlayerStats` reapplies the paralysis and burn penalties to the side
named by `hBattleTurn` after a switch of turns, which can be the enemy.
Because `hBattleTurn` at the battle menu is not modelled everywhere, a
status heal that would reapply a penalty to a paralysed or burned enemy is
refused. Other item effects (X items, Poké Doll, Full Restore, revives,
Ether) are refused.

Tests: local-ROM battles cover switching, cancelling, the withdrawal texts,
forced choices (including a fainted pick and a cancelled forced menu), run
after NO, Shift mode's offer (accepted and declined), a trainer double
faint, Potion, Max Potion, a Berry on a benched Pokémon, no-effect cases,
Antidote and PSNCUREBERRY, Parlyz Heal restoring Speed, Oak's warning and a
refused X Attack. Browser tests switch through the party menu and its
SWITCH/STATS/CANCEL submenu and use a Potion from the Items pocket. The
stats screen is not ported. No emulator comparison of these routines has
been run.