 GALAXIANS 7800 - new game (WIP)

[RevEng]

The instruction at 0xE874 is "jmp $ef65", which isn't the start of a full instruction, causing the 6502 to execute gibberish. Hacking this back to the original destination (according to a comment in the disassembly) causes the ROM to run without crashing, with the exception of the game missing the starfield. Not sure if that's because the commented destination is also wrong, or if the starfield is just another ProSystem Emulator ProProblem™.

Galaxians_G16_32K_FIX.a78

Both the original posted file (in prosystem) and this one seem to play more like Space Invaders. I only mention this in case someone thinks my meddling introduced that.

The problem was tracked down in a few minutes, thanks to the fine debugger in Mame/A7800. Another reason to switch over.

[Kurt_Woloch]

Thank you for the fix! You're right, it plays more like Space Invaders. The one on the original Gorf arcade game, as much as I can remember, did play more like Galaxian (Space Invaders having its own stage in Gorf). Actually, this version even manages to copy the inconsistent speed the arcade game runs at. And you can't die, which would make the game a bit more challenging.

 

Maybe it would have been better to hack Galaga into this game, which we already have since it was one of the 7800's launch titles. The next step up would probably be Gyruss which I actually think the 7800 would be good at doing with its capability to draw many sprites, especially in lines where there aren't any character graphics called for.

[Baby Blue Azure]

Nice Job, Rev Eng! I'll have to look at that to see how that happened and perhaps how the star field got run over. I do have A7800 on my machine, just not using it yet. Most of what I'm doing can be accomplished using the old method which we know can be dicey. Making changes at the level I am now can't/shouldn't be done that way any more. I already know that.

 

I "fixed" one of your games as well, the one you recently posted the source list to. It will be interesting to see what you're going to have to say about that one. It won't be released without your blessing but I'm too busy with other games at the moment. Ultimately it could bring in more sales for you.

 

Thx again, BBA

[Baby Blue Azure]

RevEng, following up, I downloaded your fix and it operates about the same on ProSystem 1.3G, including the existence of the starfield. The hexdump agrees with the disassembly in this case, so that's the bad news. Not looking at this code for over 2 years and just spending a few minutes on it right now, it appears the jump at $E874 is supposed to go to MOVENEXTGALAXIANS, and there are 2 of those. One at $E8CD (which you selected) and the other at $EF7B (which I just now selected). But $EF7B provides jerky entrance dance so that's no good. It's clear that this will probably bounce back to me. The next step is to scrub this situation by pairing up the original GORF with a 100% compare to its disassembly and then pair up my version with a 100% compare to its disassembly. Then and only then we'll know where we were and where we are. I don't have time for this right now, but I should have time by January 6 which is some kind of magical date. Sorry about the problem - I didn't know about any of this until I posted it. It's still a cool looking game and surely can be a viable game in the future. /BBA

[Baby Blue Azure]

Last night I began the arduous task of checking the GALAXIANS Disassy versus the bin Hexdump. May have done the task too fast but I did find the following errors:

1) The Hexdump is missing block $80XX for some reason - never saw that before. So I added that and it will be called Hexdump1 for the next release.

2) There are 2 instructions listed in the Disassy at address $8653: STA SCREEN01,X and JSR HISCORE_$8F50. The binary, which never lies, has 20 50 BF which is the JSR HISCORE_$8F50 command. Going to the HISCORE subroutine we see the first command is the STA SCREEN01,X command. So everything is there, it's just a Disassy documentation error.

3) The instruction at address $E0E2 on the Disassy doesn't match the binary. The Disassy has '90 56' but in the Hexdump it has '90 52'. I counted it out and '90 52' is correct. So the Disassy needs to be corrected. I also found this identical error in the originating GORF Disassy so that's been corrected.

 

The next step will be to check the GORF Disassy versus its Hexdump to verify if it has any other errors. In my check last night I didn't check the graphics bytes or the massive amount of DLL bytes. I can do a file compare in these two cases once both the GORF and GALAXIANS Hexdumps have been verified. Then I have a changelist that created the GALAXIANS and I will check to see if anything else looks erroneous.

 

I did try Scavone's GORF binary (checksum = BE2B) on hardware today and it does function on hardware. The GALAXIANS module on that doesn't do anything - no scoring - no bomb drops - no invader scroll down. These are all features I added to make it look and feel like a real game. It may not exactly be a bonafide "GALAXIANS' game, but it can easily be changed to anything we want once it's completed and working.

 

Next time I report I will have all these proposed checks completed and and I will have all new Disassy's and Hexdump's for both GORF and GALAXIANS. The target due date is January 6. Thanks, BBA

[Atariboy2600]

FINALLY one of my top ten 7800 game I wanted to see being made Galaxian is one of them and seeing it was on the 2600, 5200 and even XL Computer why not on the 7800 I even made box art for it

[Atariboy2600]

I even made some mockup screen shots on the 7800 look

[arcade124]

Just saw this, a couple of questions:

- Is this true Galaxian, or the Galaxians stage in Gorf?

- I wasn't around when whatever went down with Steve did, but I came across something while trying to figure out what happened: http://mdocweb.state.mi.us/OTIS2/otis2profile.aspx?mdocNumber=783598 Does this sound like him?

 

If it is, it makes sense why he was banned.

[128Kgames]

Just saw this, a couple of questions:

- Is this true Galaxian, or the Galaxians stage in Gorf?

- I wasn't around when whatever went down with Steve did, but I came across something while trying to figure out what happened: http://mdocweb.state.mi.us/OTIS2/otis2profile.aspx?mdocNumber=783598 Does this sound like him?

 

If it is, it makes sense why he was banned.

 

"Invalid search criteria"

 

On a related note, he was also working on porting UFO to the Astrocade, as well as making a more realistic version of Space Invaders for it (Astrocade). The Invaders graphics more closely resembled the arcade game, and in his version they wouldn't land on you and end the game.

 

There are some pics of his Space Invaders on the Bally Alley Yahoo group (I'd link to it but the images are blocked from my job).

 

I believe he had a version of Gorf for the Astrocade as well, but I could be confused on the system.

[Kurt_Woloch]

I even made some mockup screen shots on the 7800 look

That's a great mock-up, but the score on the right doesn't quite work out on the Atari 7800 because you've got multicolor (160 pixel per line) graphics on the left, and you can only have either 160 or 320 pixels per line for each scanline, but not both. Right now you're showing the score in hi-res and the enemy fleet in multicolor.

 

In contrast to that, on the title screen you're showing, the Galaxian logo could be in hi-res instead of low-res because it doesn't really contain multicolor, it's just made up of two monochrome stripes, and the Atari 7800 can do this nicely in hi-res mode. I thnk in this mode you could actually have up to 8 different foreground colors over one background color, but you can't mix them up too heavily because each object drawn, in this case, is only allowed to have one foreground color (and maybe one background color as well, but I'm not sure if they can be different or not).

 

How, then, are the games made who utilize hi-res with multicolor? Well, that's a different mode, but it's limited to 2 pallettes of 3 colors each in addition to the background color (as far as I know).

[Baby Blue Azure]

Well, golly Kurt W, I really don't know what the answer is. There is so much about this game I don't understand, especially the DLL's. So far we've gone from one incomplete game to yet another incomplete game. I'm just trying to get the existing docs up to snuff at the moment so we know exactly what is in both of these versions.

 

To answer arcade124's question, I hijacked the Galaxians stage of Scavone's 7800 Gorf to create the Galaxians game that you see above.

 

Thanks guys, BBA