Steal formula

[Tenkarider]

Hi!

I have to edit the steal formula, in order to make possible stealing to a monster lv 255.

So... do you know the position of the hex code that involves the chance of stealing, inside the rom?

[madsiur]

It is well documented and fun to play with:

Code:

C2/399E: A3 05        LDA $05,S   (Attacker)
C2/39A0: AA           TAX
C2/39A1: A9 01        LDA #$01
C2/39A3: 8D 01 34     STA $3401   (=1) (Sets message to "Doesn't have anything!")
C2/39A6: E0 08        CPX #$08    (Check if attacker is monster)
C2/39A8: B0 5F        BCS $3A09   (Branch if monster)
C2/39AA: C2 20        REP #$20    (Set 16-bit accumulator)
C2/39AC: B9 08 33     LDA $3308,Y (Target's stolen items)
C2/39AF: 1A           INC
C2/39B0: E2 21        SEP #$21    (Set 8-bit Accumulator AND Carry Flag)
C2/39B2: F0 4D        BEQ $3A01   (Fail to steal if no items)
C2/39B4: EE 01 34     INC $3401   (now = 2) (Sets message to "Couldn't steal!!")
C2/39B7: BD 18 3B     LDA $3B18,X (Attacker's Level)
C2/39BA: 69 32        ADC #$32    (adding 51, since Carry Flag was set)
C2/39BC: B0 1A        BCS $39D8   (Automatically steal if level >= 205)
C2/39BE: F9 18 3B     SBC $3B18,Y (Subtract Target's Level, along with an extra 1 because
                                   Carry Flag is unset at this point.  Don't worry; this
                                   cancels out with the extra 1 from C2/39BA.)

                                  (StealValue = [attacker level + 51] - [target lvl + 1]
                                   = Attacker level + 50 - Target level )

C2/39C1: 90 3E        BCC $3A01   (Fail to steal if StealValue < 0)

C2/39C3: 30 13        BMI $39D8   (Automatically steal if StealValue >= 128)
C2/39C5: 85 EE        STA $EE     (save StealValue)
C2/39C7: BD 45 3C     LDA $3C45,X
C2/39CA: 4A           LSR
C2/39CB: 90 02        BCC $39CF   (If no sneak ring)
C2/39CD: 06 EE        ASL $EE     (Double value)
C2/39CF: A9 64        LDA #$64
C2/39D1: 20 65 4B     JSR $4B65   (Random: 0 to 99)
C2/39D4: C5 EE        CMP $EE
C2/39D6: B0 29        BCS $3A01   (Fail to steal if the random number >= StealValue)
C2/39D8: 5A           PHY
C2/39D9: 20 5A 4B     JSR $4B5A   (Random: 0 to 255)
C2/39DC: C9 20        CMP #$20
C2/39DE: 90 01        BCC $39E1   (branch 1/8 of the time, so Rare steal slot
                                   will be checked)
C2/39E0: C8           INY         (Check the 2nd [Common] slot 7/8 of the time)
C2/39E1: B9 08 33     LDA $3308,Y (Target's stolen item)
C2/39E4: 7A           PLY
C2/39E5: C9 FF        CMP #$FF    (If no item)
C2/39E7: F0 18        BEQ $3A01   (Fail to steal)
C2/39E9: 8D 35 2F     STA $2F35   (Item stolen, for message purposes)
C2/39EC: 9D F4 32     STA $32F4,X (Store in "Acquired item")
C2/39EF: BD 18 30     LDA $3018,X
C2/39F2: 0C 8C 3A     TSB $3A8C   (flag character to have any applicable item in
                                   $32F4,X added to inventory when turn is over.)
C2/39F5: A9 FF        LDA #$FF
C2/39F7: 99 08 33     STA $3308,Y  (Set to no item to steal)
C2/39FA: 99 09 33     STA $3309,Y  (in both slots)
C2/39FD: EE 01 34     INC $3401    (now = 3) (Sets message to "Stole #whatever ")
C2/3A00: 60           RTS

[Tenkarider]

C2/39BE: F9 18 3B SBC $3B18,Y (Subtract Target's Level)

Ok, this should be the line that interests me, my idea was to halve the target's Level value(only for the steal formula, not halving it even in battle ), just before that SBC(maybe with a LSR?).

In this way, an high level stealer, should have some chance to steal... it doesn't seem so hard to set it, but i dunno where's stored the target's level

Could you tell me, please?

PS. Even if it becomes easier twice to steal, i don't care about that.

[Xenovant]

The line you are looking for, is this one

C2/39BA: 69 32 ADC #$32 (adding 51, since Carry Flag was set)

Change the value (32) to a higher one and you will raise the chances of a successful theft

[Tenkarider]

LoL, that's a lot easier

It must be myself that i tend to see the hard route, before the easy one

[wolfokami321]

Sorry for necroposting but does this also apply to the theif knife?

[Tenkarider]

I don't know, but i doubt they invented 2 different steal formulas...

[ShinMrKarate]

I found this code in headered rom address C2/23BBE: F9 18 3B is this code will change it or not and where!?this also code in headered rom address C2/23BBA: 69 32 in the value is [32] what is the max number to raise the chances of a successful theft even the rare items are succeed stole!?I want to be sure....

[Tenkarider]

I'm not sure about what you wanna know exactly... for editing the chances of make a succesful steal, the answer is in the posts above;
The chances of steal a common, or a rare item are a different formula.