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Disassembling 2600 Games?


DEBRO

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Oh boy, I am horrible at time estimations.  We had a medical issue in the family, so yet another year has flown by.  Time to polish off Space Invaders and get it posted before something else happens (the gods must not want it to get out)

 

Anyone else working on disassemblies lately?

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  • 11 months later...

Every time I start to get back into polishing off Space Invaders for posting online, something happens.  It's done and just needs labels / comments / cleanup -  I'm not letting this damn pandemic get in my way!

 

Anyone working on any disassemblies lately?

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Hi there,

On 7/31/2020 at 5:10 PM, LeChuck said:

Every time I start to get back into polishing off Space Invaders for posting online, something happens.  It's done and just needs labels / comments / cleanup -  I'm not letting this damn pandemic get in my way!

 

Anyone working on any disassemblies lately?

I'm just working through my TODO as I find interest and time.

 

I'm looking forward to seeing Space Invaders completed. I've been avoiding that one since you have been working on it.

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On 8/1/2020 at 7:34 PM, DEBRO said:

Hi there,

I'm just working through my TODO as I find interest and time.

 

I'm looking forward to seeing Space Invaders completed. I've been avoiding that one since you have been working on it.

Cool - it's kind of sad how long I've had it to being almost ready to post.  The house flood of 2017 really screwed things up momentum-wise, it took a couple years to fully recover from that.  Luckily I took a lot of notes of the higher-level algorithms, register usage, etc so it's pretty easy to pick back up. 

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Hope everyone is doing well!  Any disassembling going on lately?

 

I said I wouldn't let the pandemic stop me from finishing Space Invaders, but I admit it has been hard to focus on projects like this while the world is on fire around me.  Anyway, I picked my latest code back up and started going through it again this week.  The only thing it really lacks are meaningful labels/defines and a few small TBD code/data areas I marked before .. so luckily is still practically done!

 

Just to throw another bone out in the meantime ..

- The code uses bitmaps to store the remaining invaders in each row. These bitmaps gets shifted over to the right as needed so that bit 0 corresponds to the leftmost column that still has invaders remaining.

- The code also has a variable that tracks the bottom-most row that still has invaders remaining.  Among other reasons, it uses this to know how many rows of invaders to draw.

- Both of these get updated immediately when you shoot an invader.  This creates a graphic glitch when you kill the last remaining invader in the leftmost column or in the bottom row - since the code is no longer processing those rows/columns, the invader goes to black immediately and never gets a death animation.

 

I've seen that glitch my whole life, it was interesting to find out why.  There are a million little gems like that in here.  Hopefully I can actually finish this soon and make a thread to describe the findings ..

 

LeChuck

 

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2 minutes ago, LeChuck said:

I've seen that glitch my whole life, it was interesting to find out why. 

Such a glitch got me started with my first disassembly. I wanted to find out why the Starmaster score rolled so weird when I managed to save all 4 stations in the highest level.

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On 8/20/2016 at 6:01 PM, tschak909 said:

I'd request a disassembly of Video Olympics..mostly am looking at it to see how they did a nice 2x2 ball in a 2 line kernel that was smooth (I tried to do it by ANDing the scanline by #$FC, and it gets the ball size correct, but the vertical motion is quantized, so even with vertical delay, it still wobbles...) :P

 

-Thom

Is your square in Adventure 2 x 2?

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