Re: [stella] Crazy Balloon Beginner Mode

Subject: Re: [stella] Crazy Balloon Beginner Mode
From: "Fred Quimby" <c9r@xxxxxxxxxxx>
Date: Tue, 14 Jun 2005 07:57:58 -0400
I took a look at your source code and noticed something unusual.

In this code:

    CLC
    ADC BALLOON_HEIGHT
    STA balloonPtr2

    LDA balloonOffset
    CLC
    ADC balloonMoveTab,Y
    STA balloonmovPtr
    CLC
    ADC BALLOON_HEIGHT
    STA balloonmovPtr2

Shouldn't BALLOON_HEIGHT be immediate in both cases?  Just a guess.


>From: cybergoth@xxxxxxxx
>Reply-To: stella@xxxxxxxxxxxxxxxxxx
>To: stella@xxxxxxxxxxxxxxxxxx
>Subject: Re: [stella] Crazy Balloon Beginner Mode
>Date: Tue, 14 Jun 2005 04:13:08 -0400
>
>Hi Weston!
>
>Amazing analysis! If that don't helps eliminating the bug, I don't know...
>
> > Okay, I was able to see the glitch happen again, so I've included 4
> > screengrabs from z26 to give you a better idea of what it looks like
> > is causing the problem.
>
>The pictures made it, thanks!
>
>By now I know *what* has happened here, but I don't *how*
>
> > I played 2 sessions of the game, trying to repeat the glitch. In both
> > cases, the glitch did not appear until the program had been running in
> > z26 for about 10 minutes, maybe a bit longer.
>
>That is very interesting. I definitely have no timers or processes running
>that cause any special event after such a long time. Just for the record,
>which Z26 are you using (Version? &  WIN/DOS?).
>
> > I closed that session and opened the game again. After about 10
> > minutes, the glitch appeared without me moving anything!
>
>It just happened on the title screen, by doing nothing but waiting 10
>minutes ?!?
>
> > So, my guess
> > is that the problem is not connected to moving the balloon sprite, or
> > collision with the playfield.
>
>Probably not even to my code...
>
> > So it seems to be something in the program happens after it is running
> > for about 10 minutes, or something wrong with z26.
>
>I definitely have to try a lot of things now...
>I hope I can now reproduce the bug here myself.
>
> > I hope this helps. If I discover anything new, I'll be sure to let you
> > know.
>
>Thanks a million!
>
>Eric Ball wrote:
> > > It sounds to me like something ran amok and overwrote some TIA
>registers
> > > which the game only updates during power-on initialization.
>
>Yup!
>
>What IMO happens is that one of my pointers for HMOVE values gets
>corrupted. I'm setting those pointers at startup once and from then onwards
>I only tweak the LSB. Since the problem does not go away after RESET, there
>must be *something* that managed to alter the MSB somehow...
>
>Greetings,
>Manuel
>
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>


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