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Alien Swarm + JAC! fixes

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This is a 5200 version of Alien Swarm with JAC!'s fixes as described here: http://atariage.com/forums/topic/224914-alien-swarm-hack-request/

 

Instructions can be found here: http://www.atarimania.com/game-atari-400-800-xl-xe-alien-swarm_202.html

 

JAC! provided me with the source code which I've modified for the 5200 and tested on my 4-port with Atarimax Ultimate SD.

 

Edit: updated version below

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amazing work, great game Paul

just had hopes for a JAC! video about the hacking and conversion...

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After awhile of play the colors go funny and the screen goes blank but the game keeps playing unseen.

I haven't been able to get at my 5200 yet so I can try this. I'll check it out soon and see if get the same problem.

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I was able to reproduce it - it occurs when you've got far enough in the game that the snake starts planting red saucers.

 

It's a bug from the original game. There is a table of screen addresses and when it plants a saucer (at the bottom of the screen) it reads beyond the end of the table and ends up incorrectly writing to zero page locations. Once the saucer is bouncing around the screen it is fine, it is only the initial placement of it where the issue occurs.

 

The 5200 and A8 use zero page differently which is why the bug is more evident here, although it could still lead to problems on the A8 original.

 

I made the table of screen addresses longer and it now seems fine, as far as I can get in the game anyway.

 

 

as_fix.bin

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Hi there,

 

"poked" by Aking's orginal request and thanks to Paul's excellent help I managed to create a version that compiles both to 5200 and 8000/XL. It includes some more fixes (e.g. 4 digit energy) and is available here:

 

http://atariage.com/forums/topic/224914-alien-swarm-hack-request/?p=3078433

 

I hope it works on real HW. I never had a 5200 and didn't even know how the controllers work :-)

 

Now I could a least think of a video tutorial. But am actually lacking the time. Yet, the full commented source for the XL/5200 specific parts in the download will be a good start.

Edited by JAC!

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