Bill Budge posts Pinball Construction Set source code on GitHub

https://github.com/billbudge/PCS_Atari800

by ndrake • 13 years ago

143 45 13 years ago

joverholt• 13 years ago

Wow, I spent a lot of time with this game when I was eight or so. Brings back the memories. I'm pretty sure my Atari 800 is still in my parents basement. Just need to find a TV I can hook it up to...

mcphilip• 13 years ago

Same, but on the Apple II version. I remember making Rube Goldberg like pinball layouts where the ball would be guided through all sorts of paths and down to where you'd only have to hit it with the flipper every once in awhile.

Pinball Construction Set, Spy's Adventure in North America, Robot Odyssey. So many classics on the Apple II that were fun and educational.

I basically learned college level circuit design by playing Robot Odyssey as a child. For those curious, here's a part of a Let's Play trying to solve one of the earliest puzzles in the game:

http://www.youtube.com/watch?v=uNa4wivnjgs

sbarre2• 13 years ago

What language is this project in? Github doesn't seem to know what the ".S" files are...

tonyarkles• 13 years ago

That definitely looks like assembly :)

sbarre2• 13 years ago

Some googling tells me it's assembly, but it's nothing I recognize...

Thanks! you beat me to my edit.. ;-)

Macsenour2• 13 years ago

back then we really only had Assembly as an option for games. It was a speed issue more than anything else.

ndrake• 13 years ago

According to his latest Tweet, he's planning on going through the code and adding comments. https://twitter.com/billb/status/301403958415618049

joezydeco• 13 years ago

There's some nifty tricks that Budge did in the code. Just looking at this, for example:

           LDA (PARAM),Y ;JUMP TO SELECTION
           STA DOMNU6+1
           INY
           LDA (PARAM),Y
           STA DOMNU6+2
    DOMNU6 JMP $FFFF

Instead of creating a 16-bit lookup table and doing an indirect indexed branch (which I can't even remember if you can do on a 6502), Budge just modifies the code inline and lets the jump happen naturally. Very nice.

MagerValp• 13 years ago

This is probably the most common way to handle jump tables on the 6502. If you're writing ROMable code you'll have to use indirect jmp (vector) instead of selfmod. It's more efficient to split the jump table into two halves though, with the LSB in one table and the MSB in another, and access it like so:

        lda param_lo,y
        sta vector
        lda param_hi,y
        sta vector+1
  vector = * + 1
        jmp $5e1f      ; dummy address, written with selfmod

kryptiskt• 13 years ago

The awesome blog The Digital Antiquarian had a piece on Bill Budge and PCS two weeks ago:

http://www.filfre.net/2013/02/01/

VonGuard3• 13 years ago

This is spectacular. I really wish more great old game developers would do stuff like this. Not having the source code to the greatest games of our time is like having only half of the bible, or War and Peace. Or only half of Snowcrash or Neuromancer. Imagine!

Bill's also not the only developer who has this stuff in the garage. I think the IP rights are just tricky to deal with, so few developers are comfortable dumping this stuff into github yet.

nja• 13 years ago

I totally agree! I'd love to see the source code for the original Rollercoaster Tycoon, for example. From what I understand, it's 99% assembly with a few parts in C to handle media. It would be awesome to try to grok that!

jacobparker2• 13 years ago

Well, uh, you can view that alleged 99% with a disassembler ;) (missing labels, comments, etc. though.)

barbs• 13 years ago

I agree! I was pretty pleased when Jordan Mechner found and posted the source to Prince of Persia

https://github.com/jmechner/Prince-of-Persia-Apple-II

fuzzix• 13 years ago

Maz Spork released the Z80 ASM source[0] of Buggy Boy[1] for 128K Spectrum, though it since disappeard from his site.

More of this type of thing!

[0] http://web.archive.org/web/20030629124143/http://maz.spork.d...

[1] http://www.worldofspectrum.org/infoseekid.cgi?id=0000746

tmoertel• 13 years ago

Although it's the source code for the Atari 800 version of PCS, it seems to have been built on an Apple II. From MAKE1 [1] for example:

    CALL -151
    3F2:69 FF 5A
    BLOAD GPAK.OBJ,A$1300
    BLOAD CDRAW.O,A$2480
    BLOAD PCSA800.PIC,A$2B00
    BLOAD DLIST.O,A$4910
    BLOAD SWAP.O,D2,A$4A00
    BLOAD TST.O,D1,A$4B00
    BLOAD GOATARI.O,D2,A$4B45
    BLOAD BOOT.O,D2,A$8E00
    BLOAD BOOT2.O,A$8E80
    BLOAD ZAP1.O,A$8F00
    BLOAD DOWNLOAD.O,D1,A$300

The first line invokes the Apple II "System Monitor", the second writes 3 bytes to memory at address $3F2 (the effect of which is to tell the computer to enter the Monitor whenever someone resets the computer from the keyboard), and the rest load binary files into different memory areas. I'm guessing it's all to build an image to be written to disk. (See [2] for more on the System Monitor.)

[1] https://github.com/billbudge/PCS_Atari800/blob/master/Disk1/...

[2] http://apple2.info/wiki/index.php?title=System_Monitor#Gener...

EDIT: added additional details

thought_alarm• 13 years ago

It looks like he used an Apple II as the development environment, which is straight forward since both machines use the same CPU. The .S files are assembled to 6502 object files. The "makefile" loads each object file to a specific area in RAM, then Download.o transfers the contents of RAM to a waiting Atari 800 via serial connection.

js2• 13 years ago

And a development session would have looked somewhat like this:

http://www.youtube.com/watch?v=CDPlfqpgW8c

(I may miss the Merlin assembler, but I don't miss disk ][ drives at all.)

Macsenour2• 13 years ago

At Broderbund we used Apple II's to develop for both the Atari 800 and the C64. I worked on a cable and software for both ends so we wouldn't have to change systems. It is MUCH faster to develop on one machine, and test on another.

johansch• 13 years ago

Here's Bill demoing this game in 1984:

https://www.youtube.com/watch?feature=player_detailpage&...

drudru112• 13 years ago

It is cool that people are doing this (Karateka, etc.)

lysol• 13 years ago

I wish that someone would find Stuart Smith and get him to do the same with Adventure Construction Set.

binarycrusader2• 13 years ago

I'm thankful the author did this, but there's no copyright notice or license.

Obviously I can assume it's copyrighted, but it would be nice to have the explicit declarations.

tptacek3• 13 years ago

gojomo3• 13 years ago

True. And yet: the author has overtly placed it in a public place normally understood to be for sharing.

At the very least, people can reasonably assume an implicit permission to do the usual things that are done with Github public repositories: fork at Github, create local copies, create derivatives with the intent of sharing back to the original, etc.

And, if he's using Github's free plan, that's only available for projects that are "open source", a term with a fairly well-understood meaning in our profession. So he's likely also implicitly represented to Github that whatever the formal license, it qualifies as 'open source'.

The author could be confused. It could be a trap. He could probably withdraw any of these implicit permissions by taking the right explicit future steps.

But in the meantime, people don't have to fear normal copying and sharing based on a default 'all rights reserved' assumption. It's probably OK, and even if the author changes his assertions later, penalties for copying during this 'implied consent' period are unlikely.

binarycrusader2• 13 years ago

The author has since added a MIT license to the repository. Yea!

beernutz• 13 years ago

This is great! I really wish there were a developer commentary track that you could listen to as you read the source code. Would be really cool to hear what they thought about with specific routines, or neat hacks they used to make things work in small memory footprints like that.

lec• 13 years ago

This is a masterpiece of early programming. I am very grateful he is posting the source.

unwind• 13 years ago

This is cool. Not so sure about the practice of committing object files to source control, but I guess it makes sense in a "the more, the better" kind of way, at least.

As a side note, I must say that as a former (contracting) developer at an EA studio, it's a very interesting feeling to see the programmer (the programmer, as in "the one") of a recent release sit next to EA's boss and talk about the title.

Things have certainly moved on a bit, since then. :)

Bill Budge posts Pinball Construction Set source code on GitHub

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