pokecrystal-board/engine/battle/start_battle.asm

ShowLinkBattleParticipants: ; 2ee18
; If we're not in a communications room,
; we don't need to be here.
	ld a, [wLinkMode]
	and a
	ret z

	farcall _ShowLinkBattleParticipants
	ld c, 150
	call DelayFrames
	call ClearTileMap
	call ClearSprites
	ret

FindFirstAliveMonAndStartBattle: ; 2ee2f
	xor a
	ld [hMapAnims], a
	call DelayFrame
	ld b, 6
	ld hl, PartyMon1HP
	ld de, PARTYMON_STRUCT_LENGTH - 1

.loop
	ld a, [hli]
	or [hl]
	jr nz, .okay
	add hl, de
	dec b
	jr nz, .loop

.okay
	ld de, MON_LEVEL - MON_HP
	add hl, de
	ld a, [hl]
	ld [BattleMonLevel], a
	predef DoBattleTransition
	farcall _LoadBattleFontsHPBar
	ld a, 1
	ld [hBGMapMode], a
	call ClearSprites
	call ClearTileMap
	xor a
	ld [hBGMapMode], a
	ld [hWY], a
	ld [rWY], a
	ld [hMapAnims], a
	ret

PlayBattleMusic: ; 2ee6c
	push hl
	push de
	push bc

	xor a
	ld [MusicFade], a
	ld de, MUSIC_NONE
	call PlayMusic
	call DelayFrame
	call MaxVolume

	ld a, [BattleType]
	cp BATTLETYPE_SUICUNE
	ld de, MUSIC_SUICUNE_BATTLE
	jp z, .done
	cp BATTLETYPE_ROAMING
	jp z, .done

	; Are we fighting a trainer?
	ld a, [OtherTrainerClass]
	and a
	jr nz, .trainermusic

	farcall RegionCheck
	ld a, e
	and a
	jr nz, .kantowild

	ld de, MUSIC_JOHTO_WILD_BATTLE
	ld a, [TimeOfDay]
	cp NITE_F
	jr nz, .done
	ld de, MUSIC_JOHTO_WILD_BATTLE_NIGHT
	jr .done

.kantowild
	ld de, MUSIC_KANTO_WILD_BATTLE
	jr .done

.trainermusic
	ld de, MUSIC_CHAMPION_BATTLE
	cp CHAMPION
	jr z, .done
	cp RED
	jr z, .done

	; They should have included EXECUTIVEM, EXECUTIVEF, and SCIENTIST too...
	ld de, MUSIC_ROCKET_BATTLE
	cp GRUNTM
	jr z, .done
	cp GRUNTF
	jr z, .done

	ld de, MUSIC_KANTO_GYM_LEADER_BATTLE
	farcall IsKantoGymLeader
	jr c, .done

	; IsGymLeader also counts CHAMPION, RED, and the Kanto gym leaders
	; but they have been taken care of before this
	ld de, MUSIC_JOHTO_GYM_LEADER_BATTLE
	farcall IsGymLeader
	jr c, .done

	ld de, MUSIC_RIVAL_BATTLE
	ld a, [OtherTrainerClass]
	cp RIVAL1
	jr z, .done
	cp RIVAL2
	jr nz, .othertrainer

	ld a, [OtherTrainerID]
	cp RIVAL2_2_CHIKORITA ; Rival in Indigo Plateau
	jr c, .done
	ld de, MUSIC_CHAMPION_BATTLE
	jr .done

.othertrainer
	ld a, [wLinkMode]
	and a
	jr nz, .johtotrainer

	farcall RegionCheck
	ld a, e
	and a
	jr nz, .kantotrainer

.johtotrainer
	ld de, MUSIC_JOHTO_TRAINER_BATTLE
	jr .done

.kantotrainer
	ld de, MUSIC_KANTO_TRAINER_BATTLE

.done
	call PlayMusic

	pop bc
	pop de
	pop hl
	ret

ClearBattleRAM: ; 2ef18
	xor a
	ld [wPlayerAction], a
	ld [wBattleResult], a

	ld hl, wPartyMenuCursor
	ld [hli], a
	ld [hli], a
	ld [hli], a
	ld [hl], a

	ld [wMenuScrollPosition], a
	ld [CriticalHit], a
	ld [BattleMonSpecies], a
	ld [wBattleParticipantsNotFainted], a
	ld [CurBattleMon], a
	ld [wForcedSwitch], a
	ld [TimeOfDayPal], a
	ld [PlayerTurnsTaken], a
	ld [EnemyTurnsTaken], a
	ld [EvolvableFlags], a

	ld hl, PlayerHPPal
	ld [hli], a
	ld [hl], a

	ld hl, BattleMonDVs
	ld [hli], a
	ld [hl], a

	ld hl, EnemyMonDVs
	ld [hli], a
	ld [hl], a

; Clear the entire BattleMons area
	ld hl, wBattle
	ld bc, wBattleEnd - wBattle
	xor a
	call ByteFill

	callfar ResetEnemyStatLevels

	call ClearWindowData

	ld hl, hBGMapAddress
	xor a ; LOW(vBGMap0)
	ld [hli], a
	ld [hl], HIGH(vBGMap0)
	ret