Astroblast 100k bug

[cwieland]

Hi.  I was playing the HSC NTSC version of Astroblast and encountered the bug that incorrectly gives you extra lives when you go over a 100k then fall below 100k.  Every object you shoot while below 100k turns into an extra life.  I think there is a version of the game where this bug has been fixed.  If so, it would nice if we could incorporate this fix into the HSC version.

 

 

Edited November 18, 2021 by cwieland

[cwieland]

Disregard this.  I was playing around with Stella and the "fixed" version of the game apparently didn't fix this bug either.

[+Al_Nafuur]

I used @DEBRO's disassembly from bjars.com for the HSC conversion. I can't find any hints about this bug and a "fixed" version in the code.

 

[+Al_Nafuur]

As far as I understand the text at Atari Compendium:

http://www.ataricompendium.com/game_library/easter_eggs/vcs/26astroblast.html

 

there had been two versions, but only the "two joysticks" bugs have been fixed in the second version.

[cwieland]

I think this would fix it.  But since it's like that in the original game, I wonder if we should or not.

.incrementScoreLoop
   ...
   lda playerScore + 1              ; get player hundreds value
   beq CheckToIncrementNumberOfBases
   cmp peakScore+1
   beq .checkToSetNewPeakScore
   bcc .checkToSetNewPeakScore
   
   ; 100k points bug fix
   ; This bug occurs when the score has gone past a 100k mark (e.g. 100000, 200000, etc.) and subsequently drops
   ; below the 100k mark.  An extra base is awarded until the 100k mark is reached again or the player has 99 bases.
   
   ; At this point in the logic we know that the player hundreds value is greater than the peak hundreds value.
   ; This additional logic ensures that the player thousands value is also equal to or greater the peak thousands value.

   lda playerScore                  ; get player thousands value
   cmp peakScore                    
   bcc .checkToSetNewPeakScore      ; Prevent running extra man logic if player thousands score is less than peak score thousands

.incrementNumberOfBases
   ...

 

Edited November 19, 2021 by cwieland
My grammar sucks

[+Al_Nafuur]

On 11/19/2021 at 3:51 AM, cwieland said:

I think this would fix it.  But since it's like that in the original game, I wonder if we should or not.

.incrementScoreLoop
   ...
   lda playerScore + 1              ; get player hundreds value
   beq CheckToIncrementNumberOfBases
   cmp peakScore+1
   beq .checkToSetNewPeakScore
   bcc .checkToSetNewPeakScore
   
   ; 100k points bug fix
   ; This bug occurs when the score has gone past a 100k mark (e.g. 100000, 200000, etc.) and subsequently drops
   ; below the 100k mark.  An extra base is awarded until the 100k mark is reached again or the player has 99 bases.
   
   ; At this point in the logic we know that the player hundreds value is greater than the peak hundreds value.
   ; This additional logic ensures that the player thousands value is also equal to or greater the peak thousands value.

   lda playerScore                  ; get player thousands value
   cmp peakScore                    
   bcc .checkToSetNewPeakScore      ; Prevent running extra man logic if player thousands score is less than peak score thousands

.incrementNumberOfBases
   ...

 

Many thanks for the code. I have build a "fixed" version of the HSC ROM, which was a bit of work because I had to split up the PlusROM send function to fit all in.

 

The fixed version is uploaded to the PlusStore folder: /Public ROMs/PlusROMs/High Score Club

 

The code can be found at : https://github.com/Al-Nafuur/PlusROM-Hacks/blob/main/High Score Club hacks/Astroblast HSC/Astroblast HSC.asm

 

Unfortunately I am not very good at Astroblast, so I can not test the fix.

 

[cwieland]

Cool I'll give it a try.  You should probably remove my 166k score from yesterday since I unintentionally exploited the bug to get it. ?

Edited November 21, 2021 by cwieland

[+Al_Nafuur]

3 hours ago, cwieland said:

Cool I'll give it a try. 

?

3 hours ago, cwieland said:

You should probably remove my 166k score from yesterday since I unintentionally exploited the bug to get it. ?

done

[cwieland]

I can't get to 100k today.  There must be something wrong with my paddles ?

[cwieland]

It looks like there may be a bug in the logic that sends the score.  I had the difficulty switches set to B/B when I got the scores below.  I think that those should have come in as "Amateur" instead of "Expert".

 

[+Al_Nafuur]

21 hours ago, cwieland said:

It looks like there may be a bug in the logic that sends the score.  I had the difficulty switches set to B/B when I got the scores below.  I think that those should have come in as "Amateur" instead of "Expert".

 

Looks like I have done a mistake in the ROM and send the gameLevel variable, but for the "Amateur" setting this variable increases with the scores..

 

[cwieland]

I looked at this bit yesterday too.  Perhaps you could just send a fake level for Expert instead of having to retool everything.  Just an idea.

SendPlusROMScore:
   ldx #2
   bit SWCHB                        ; Get the value of the right difficulty switch
   bpl .sendGameLevelForAmateur
   lda #$FF                         ; Use level "FF" when right difficulty switch is set to A (expert)
   sta gameLevel

.sendGameLevelForAmateur
   lda gameLevel
   sta WriteToBuffer
   ...

Never mind, too many bytes...

Edited November 27, 2021 by cwieland

[+Al_Nafuur]

35 minutes ago, cwieland said:

I looked at this bit yesterday too.  Perhaps you could just send a fake level for Expert instead of having to retool everything.  Just an idea.

SendPlusROMScore:
   ldx #2
   bit SWCHB                        ; Get the value of the right difficulty switch
   bpl .sendGameLevelForAmateur
   lda #$FF                         ; Use level "FF" when right difficulty switch is set to A (expert)
   sta gameLevel

.sendGameLevelForAmateur
   lda gameLevel
   sta WriteToBuffer
   ...

Never mind, too many bytes...

 

 

instead of :

SendPlusROMScore:
   lda gameLevel
   sta WriteToBuffer

we could send SWCHB:

SendPlusROMScore:
   lda SWCHB                        ; Get the value of the right difficulty switch
   sta WriteToBuffer

the rest can be done at the HSC backend.

 

Currently gameLevel is 4 for "Expert" and 0 for "Amateur". The value sent is right shifted at the backend 2 times, so we have 0 = Amateur and 1 = Expert in the database. For this new version we would have to do a right shift 7 times in the backend transformation.

 

But changing the transformation in the backend and the data sent by the ROM also means we have to change the game-id, so old versions of the ROM, that have been downloaded by users and are still used locally, will not sent wrong data to the new transformation.

 

To avoid this we might try something like this:

SendPlusROMScore:
   lda SWCHB                        ; Get the value of the right difficulty switch
   lsr
   lsr
   lsr
   lsr
   lsr
   sta WriteToBuffer
   ...

 

 

[+Al_Nafuur]

I have build a new version of the HSC ROM.

 

After thinking about it a bit, I came to the conclusion to use the variant with the new transformation in the backend. If we would have right shifted SWCHB in the new ROM version and leave the Transformation as is, then users of the old ROM version would have an advantage, because some of their "Amateur" games would have been listed as "Expert" games in the HSC. Using a new Transformation instead means that users of the old version would have no advantage (only the disadvantage that all their games will be listed as "Amateur")

 

On 11/26/2021 at 8:41 PM, cwieland said:

It looks like there may be a bug in the logic that sends the score.  I had the difficulty switches set to B/B when I got the scores below.  I think that those should have come in as "Amateur" instead of "Expert".

 

?

I switched these scores to "Amateur" in the HSC database.

[cwieland]

Both bug fixes are confirmed.  I dipped below 100k and did not get any extra bases after getting back to 100k.