First Commit

Upload literally everything from the pokecrystal16 expand-move-ID branch

engine/battle/move_effects/counter.asm

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+BattleCommand_Counter:
+	ld a, 1
+	ld [wAttackMissed], a
+	ld a, BATTLE_VARS_LAST_COUNTER_MOVE_OPP
+	call GetBattleVar
+	and a
+	ret z
+
+	ld b, a
+	callfar GetMoveEffect
+	ld a, b
+	cp EFFECT_COUNTER
+	ret z
+
+	call BattleCommand_ResetTypeMatchup
+	ld a, [wTypeMatchup]
+	and a
+	ret z
+
+	call CheckOpponentWentFirst
+	ret z
+
+	ld a, BATTLE_VARS_LAST_COUNTER_MOVE_OPP
+	call GetBattleVar
+	ld de, wStringBuffer1
+	call GetMoveData
+
+	ld a, [wStringBuffer1 + MOVE_POWER]
+	and a
+	ret z
+
+	ld a, [wStringBuffer1 + MOVE_TYPE]
+	cp SPECIAL
+	ret nc
+
+; BUG: Counter and Mirror Coat still work if the opponent uses an item (see docs/bugs_and_glitches.md)
+	ld hl, wCurDamage
+	ld a, [hli]
+	or [hl]
+	ret z
+
+	ld a, [hl]
+	add a
+	ld [hld], a
+	ld a, [hl]
+	adc a
+	ld [hl], a
+	jr nc, .capped
+	ld a, $ff
+	ld [hli], a
+	ld [hl], a
+.capped
+
+	xor a
+	ld [wAttackMissed], a
+	ret