1 files changed, 197 insertions, 0 deletions
diff --git a/engine/start_battle.asm b/engine/start_battle.asm
new file mode 100644
index 000000000..51f46b3f2
--- /dev/null
+++ b/engine/start_battle.asm
@@ -0,0 +1,197 @@
+ShowLinkBattleParticipants: ; 2ee18
+; If we're not in a communications room,
+; we don't need to be here.
+	ld a, [wLinkMode]
+	and a
+	ret z
+
+	callba _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 Predef_StartBattle
+	callba _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
+
+	callba 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
+
+	; really, they should have included admins and scientists here too...
+	ld de, MUSIC_ROCKET_BATTLE
+	cp GRUNTM
+	jr z, .done
+	cp GRUNTF
+	jr z, .done
+
+	ld de, MUSIC_KANTO_GYM_LEADER_BATTLE
+	callba IsKantoGymLeader
+	jr c, .done
+
+	ld de, MUSIC_JOHTO_GYM_LEADER_BATTLE
+	callba IsJohtoGymLeader
+	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
+
+	callba 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
+
+	callab ResetEnemyStatLevels
+
+	call ClearWindowData
+
+	ld hl, hBGMapAddress
+	xor a
+	ld [hli], a
+	ld [hl], VBGMap0 / $100
+	ret