Automatically reuse Repel

Starting in B2/W2, when a Repel, Super Repel, or Max Repel expires and you have another one of the same type, the "Repel's effect wore off…" message will be followed by the option to use another.

Implementing this feature in Gen 2 is relatively simple, but does involve a number of different areas:

• WRAM and SRAM need space to save the type of Repel
• The Repel item effect needs to save its type
• The script that notifies when a Repel wears off needs to check if you have another one and let you choose to reuse it
• There needs to be an alternative notification message including the "Use another?" question text

1. Add space in RAM for wRepelType

There's already this line in wram.asm:

wRepelEffect:: db ; If a Repel is in use, it contains the nr of steps it's still active

It's between the wPlayerData and wPlayerDataEnd labels. That means it's part of the saved data, so resetting the game will still remember how many Repel steps you have left.

We need to add a wRepelType byte that works the same way. It's just one byte since it stores the item ID. There's free space nearby, so let's use that:

wLuckyNumberShowFlag:: db ; dc9d
-	ds 1
+wRepelType:: db
wLuckyIDNumber:: dw ; dc9f

wRepelEffect:: db ; If a Repel is in use, it contains the nr of steps it's still active
wBikeStep:: dw
wKurtApricornQuantity:: db

2. Store wRepelType when a Repel is used

The file that defines item effects is, predictably, engine/item_effects.asm. It turns out that Repel, Super Repel, and Max Repel all use the same code, so we don't have to write anything three times.

SuperRepel: ; f462
	ld b, 200
	jr UseRepel
; f466

MaxRepel: ; f466
	ld b, 250
	jr UseRepel
; f466

Repel: ; f46a
	ld b, 100
; f46c

UseRepel: ; f46c
	ld a, [wRepelEffect]
	and a
	ld hl, TextJump_RepelUsedEarlierIsStillInEffect
	jp nz, PrintText

	ld a, b
	ld [wRepelEffect], a
+	ld a, [wCurItem]
+	ld [wRepelType], a
	jp UseItemText


TextJump_RepelUsedEarlierIsStillInEffect: ; 0xf47d
	; The REPEL used earlier is still in effect.
	text_jump Text_RepelUsedEarlierIsStillInEffect
	db "@"
; 0xf482

3. Ask whether to reuse Repel

Edit engine/events.asm:

DoRepelStep: ; 96bd7
	ld a, [wRepelEffect]
	and a
	ret z

	dec a
	ld [wRepelEffect], a
	ret nz

+	ld a, [wRepelType]
+	ld [wCurItem], a
+	ld hl, wNumItems
+	call CheckItem
	ld a, BANK(RepelWoreOffScript)
	ld hl, RepelWoreOffScript
+	jr nc, .got_script
+	ld a, BANK(UseAnotherRepelScript)
+	ld hl, UseAnotherRepelScript
+.got_script
	call CallScript
	scf
	ret
; 96beb

Note that UseAnotherRepelScript hasn't been defined yet, so we'll do that next.

4. Define UseAnotherRepelScript

Edit engine/events/misc_scripts_2.asm:

RepelWoreOffScript:: ; 0x13619
	opentext
	writetext .text
	waitbutton
	closetext
	end

.text ; 0x13620
	; REPEL's effect wore off.
	text_jump UnknownText_0x1bd308
	db "@"

+UseAnotherRepelScript::
+	opentext
+	writetext .text
+	yesorno
+	iffalse .done
+	callasm DoItemEffect
+.done
+	closetext
+	end
+
+.text:
+	text_jump UseAnotherRepelText
+	db "@"

Again, we have not yet defined UseAnotherRepelText, so let's finish up with that.

5. Define UseAnotherRepelText

Edit data/text/common_1.asm:

UnknownText_0x1bd308::
	text "REPEL's effect"
	line "wore off."
	done

+UseAnotherRepelText::
+	text "REPEL's effect"
+	line "wore off."
+
+	para "Use another?"
+	done

Finally, the feature works!