Download DD2 Enemy HP Recovery Bugfix ROM Hack

Deep Dungeon II: Yuushi no Monshou Enemy Recovery Bugfix

In DD2, the kusa no tsuyu, or Vegetable soup can be eaten by
either the player or enemies to recover HP.
However, the code to restore the enemy's HP will in most cases
restore full HP. The code suggests that is a bug.
So, this patch will fix the behavior.

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APPLICATION NOTES
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THIS PATCH IS FOR THE JAPANESE VERSION OF THE GAME.
The upcoming English patch will include the fix, as well as an
un-fix in case some purists out there want to play the game
as is.
This patch is designed for an .fds image WITHOUT a fwNES header.
(total filesize 131,000 bytes)
If your file has a header, use a hex editor and delete the first
16 bytes.

For the IPS version of the patch, use Lunar IPS to apply it.
For the UPS version (which can patch and un-patch), use tsukuyomi (from byuu.org).

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THE BUGGY CODE
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Here's the original code to increase the enemy's current HP:
LDA $50		;random value
CLC
ADC $A447	;add to low byte
STA $A447	;store to low byte
LDA $A448
ADC #$00
STA $A448	;store high byte
CMP $A44A	;compare to max, high
BCC FillHPtoMax	;BUG! Carry is clear if Current High < Max High
;below code is run if Current High >= Max High
BNE End		;branch to end if Current High > Max High
;below code is run if Current High == Max High
LDA $A447	;current low
CMP $A449	;compare to max low
BNE FillHPtoMax	;BUG! Since the high bytes have been determined equal, now we'll fill if the low bytes aren't as well?
End:
JMP $74AD	;exit the routine
FillHPtoMax:
LDA $A449	;max low
STA $A447	;current low
LDA $A44A	;max high
STA $A448	;current high
JMP $74AD	;exit the routine
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THE FIXED CODE
--------------
Branches corrected.
LDA $50		;random value
CLC
ADC $A447	;add to low byte
STA $A447	;store to low byte
LDA $A448
ADC #$00
STA $A448	;store high byte
CMP $A44A	;compare to max, high
BEQ CompareLowBytes	;high bytes equal, so we'll need to check the low bytes
BCC End		;CORRECTED! Branch out of the routine if current high < max high
;below code is run if Current High == Max High
CheckLowBytes:
LDA $A447	;current low
CMP $A449	;compare to max low
BCS FillHPtoMax	;CORRECTED! Branch to HP fill routine if current low > max low
End:
JMP $74AD	;exit the routine
FillHPtoMax:
LDA $A449	;max low
STA $A447	;current low
LDA $A44A	;max high
STA $A448	;current high
JMP $74AD	;exit the routine