Add subdirectories to engine/ similar to pokecrystal

engine/battle/move_effects/one_hit_ko.asm

@@ -0,0 +1,38 @@
+OneHitKOEffect_:
+	ld hl, wDamage
+	xor a
+	ld [hli], a
+	ld [hl], a ; set the damage output to zero
+	dec a
+	ld [wCriticalHitOrOHKO], a
+	ld hl, wBattleMonSpeed + 1
+	ld de, wEnemyMonSpeed + 1
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .compareSpeed
+	ld hl, wEnemyMonSpeed + 1
+	ld de, wBattleMonSpeed + 1
+.compareSpeed
+; set damage to 65535 and OHKO flag is the user's current speed is higher than the target's
+	ld a, [de]
+	dec de
+	ld b, a
+	ld a, [hld]
+	sub b
+	ld a, [de]
+	ld b, a
+	ld a, [hl]
+	sbc b
+	jr c, .userIsSlower
+	ld hl, wDamage
+	ld a, $ff
+	ld [hli], a
+	ld [hl], a
+	ld a, $2
+	ld [wCriticalHitOrOHKO], a
+	ret
+.userIsSlower
+; keep damage at 0 and set move missed flag if target's current speed is higher instead
+	ld a, $1
+	ld [wMoveMissed], a
+	ret