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Bits and Bytes: My 7800 programming tests and demos


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I'm in the "games are art" camp, and I see these sorts of works as not that much different than a study...


In our case, composition and technique is usually hidden away in the code.

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Hey gang! I'm trying to work on Space Invaders from the original source code and so far have only found this link: https://computerarcheology.com/Arcade/SpaceInvaders/Code.html


Does anyone else have a fully decompiled or source code for Space Invaders? I'm going to be rewriting it in 7800Basic/6502 assembler and I'm trying to be as true as possible to the original code. I wonder if Bob Decrescenzo had the source code when he ported Space Invaders to the 7800 (which is absolutely incredible).


@Muddyfunster that makes me feel somewhat better. You and a handful of the other devs give me a goal for which to strive.


I really need to work on POKEY code since I am a classically trained musician. I also love the YM2149F/AY-3-8910 and would love to work with them on the 7800. I have a couple of spare AY-3-8910s lying around that I need to test, setup, and run on a Raspberry Pi/Arduino setup to play some classic chip tunes. Growing up in the States I never got exposed to the ZX Spectrum that much and absolutely fell in love with the tunes that the later models could play. I love that sound and grew up hearing those chips in Tron, Discs of Tron, and so many more.

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  • 1 month later...

1625592062_Screenshotfrom2023-02-0701-02-19.thumb.png.eed217dd39c6373962cf7f62d3c51964.pngEwe Snooze

This is an unusual one, bur the Mario Party games had this little "gaddget" in it called "Snooze Ewes" that featured sheep jumping over a fence that was intended to be relaxing and to help with sleep. I thought this would be a fun little project on the 7800.

I tried to create the gradient effect in the background sky, and it worked until I added the POKEY player and the interrupts for the top and bottom screen routines interfered.

I stole the "Daisy" music from one of the demos for 7800basic and will update it with my own composition soon.


Original "Snooze Ewes"



JS7800 Link: https://raz0red.github.io/js7800/?cart=https://forums.atariage.com/applications/core/interface/file/attachment.php?id=999893&key=254fe3de97af58f8493b1513713f7b72


Edited by saxmeister
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  • 1 month later...


In my quest to re-code the original Atari/Kee arcade games from the early 1970s, I took on "Breakout." The original game is only TTL circuits, so no code/CPU. I thought I would try to see how close I could get to the original arcade version on the 7800. Here is a very rough, very early work-in-progress.


No sound, barely any game logic beyond hitting and hiding the bricks. The normal different angles aren't in code yet. Everything is at 45 degree angles for now. This will be fixed.



My idea is to bundle the entire lot of Pong related games into one cart. Everything including Pong, Pong Doubles, Rebound/Spike, Quadpong, Breakout, etc. 


JS7800 Link: https://raz0red.github.io/js7800/?cart=https://forums.atariage.com/applications/core/interface/file/attachment.php?id=1011986&key=1baaa10c731f907a1ba647ffa6cfd974





Edited by saxmeister
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Nice start. Btw, I played it with a joystick and that works as expected.  I also tried a 2nd game with paddles. The paddles are recognized, however you move left & right by holding down the left & right fire buttons. I'm guessing that the paddle logic really hasn't been implemented yet.  Thanks for sharing.🙂 

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@sramirez2008 you are correct. I have not implemented any paddle logic yet. I only currently have Commodore paddles and a non-working Atari 7800, so it's all been code in the virtual world. I've got to get that code implemented, especially for the analog control over the paddle!


Sooooooooo much to optimize!


UPDATE: I am in the process of moving and stepped on my 40 year old Commodore paddles and smashed one to bits. Not a happy moment for me. So, I am currently "paddle-less."

Edited by saxmeister
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  • 4 months later...

SORRY ALL! Posted this in the wrong window. This was meant to be in another thread.


Testing 160B with 4- and 6-color graphics using Cannon Fodder graphics. Hit fire to switch between the two graphics and palettes.




JS7800 Link: https://raz0red.github.io/js7800/?cart=https://forums.atariage.com/applications/core/interface/file/attachment.php?id=1043193&key=2bbc1072add2a98b99b98648d6b71905



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  • 7 months later...

First Scrolling Experiment: Horizontal

I've been reading up on scrolling techniques for the 7800 and decided to do some testing with what is currently baked into 7800BASIC. So far things are looking good.


In the demo, push the joystick left to scroll left, push right to scroll right, and press any fire to stop the motion.


JS7800 Link: https://raz0red.github.io/js7800/?cart=https://forums.atariage.com/applications/core/interface/file/attachment.php?id=1098356&key=216d9f6ce747f736cf087d5a8ca74473





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