1 files changed, 144 insertions, 0 deletions
diff --git a/engine/battle/start_battle.asm b/engine/battle/start_battle.asm
new file mode 100755
index 00000000..7627a100
--- /dev/null
+++ b/engine/battle/start_battle.asm
@@ -0,0 +1,144 @@
+PlayBattleMusic:
+	push hl
+	push de
+	push bc
+
+	xor a
+	ld [wMusicFade], a
+	ld de, MUSIC_NONE
+	call PlayMusic
+	call DelayFrame
+	call MaxVolume
+
+	; Are we fighting a trainer?
+	ld a, [wOtherTrainerClass]
+	and a
+	jr nz, .trainermusic
+
+	farcall RegionCheck
+	ld a, e
+	and a
+	jr nz, .kantowild
+
+	ld de, MUSIC_JOHTO_WILD_BATTLE
+	ld a, [wTimeOfDay]
+	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, [wOtherTrainerClass]
+	cp RIVAL1
+	jr z, .done
+	cp RIVAL2
+	jr nz, .othertrainer
+
+	ld a, [wOtherTrainerID]
+	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:
+	xor a
+	ld [wBattlePlayerAction], a
+	ld [wBattleResult], a
+
+	ld hl, wPartyMenuCursor
+	ld [hli], a
+	ld [hli], a
+	ld [hli], a
+	ld [hl], a
+
+	ld [wMenuScrollPosition], a
+	ld [wCriticalHit], a
+	ld [wBattleMonSpecies], a
+	ld [wBattleParticipantsNotFainted], a
+	ld [wCurBattleMon], a
+	ld [wForcedSwitch], a
+	ld [wTimeOfDayPal], a
+	ld [wPlayerTurnsTaken], a
+	ld [wEnemyTurnsTaken], a
+	ld [wEvolvableFlags], a
+
+	ld hl, wPlayerHPPal
+	ld [hli], a
+	ld [hl], a
+
+	ld hl, wBattleMonDVs
+	ld [hli], a
+	ld [hl], a
+
+	ld hl, wEnemyMonDVs
+	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