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Space Invaders Arcade

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2 hours ago, SpiceWare said:


This artifact?











I apologize, I thought we were looking for pixels within the game (square grid) itself. I can see this artifact, but only on my Harmony and Harmony Encore. The ROM displays differently (please see below) via the UnoCart. 


Harmony/Harmony Encore 





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7 minutes ago, Thomas Jentzsch said:

No, you assumed right the first time. We are looking for the pixel in the game square.

Okay, then I stand by my original statement.  The pixels in the game square were fine. Sorry for the fuzzy pics.

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late PAL Jr. console (1991):

and with  the test rom by Spiceware posted in this thread:




Back to "Space Invaders"...
I tested all 3 versions on that same console with Harmony cart (doubled up v. 0.1 and 0.2 to 8k and added extension "F8S").

They work, but what's up with those stripes (playfield, I guess) on the background? They don't appear in Stella. Moreover, shots are gray instead of the sprite color (green on Stella, blue on my hardware because of PAL colors).

Those stripes are visible also in alfredtdk's screenshots posted earlier.

The score starts on the very first visible line on my TV, but it's fully visible.






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17 minutes ago, alex_79 said:

They work, but what's up with those stripes (playfield, I guess) on the background?

Right difficulty switch, for debugging reasons. :) 


I started this project with z26, which didn't have the excellent debugger of Stella.

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  • 3 weeks later...
  • 1 month later...
On 6/19/2020 at 3:20 PM, Thomas Jentzsch said:

Pixel 79 (the one left of the middle of the screen) sticks out. It has a different color. 


If you can see it (partially, complete, on/off...), please take a picture or video (and maybe add a brief description) of the game screen where the color artifact should be most obvious. Also please tell us your hardware setup. Thanks!


BTW: If your system has no color artifact, we don't need a picture. :) 


I see the artifact on my 2800 (NTSC, of course). This system has rev. D of the UAV mod installed. It also shows up during gameplay.



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  • 1 year later...

Apologies in advance if this idea is not even remotely possible...


In the arcade version, each "wave" of invaders is more difficult to defeat, because they start one row closer each time. This works, because SI displays in portrait orientation, so there is a lot of "room" for the invaders to advance. In the original VCS port, the columns of invaders are reduced from eleven to six, but the one-row-closer idea remains, meaning that the invaders remove the shields after the first, what? four or five waves? After that, the advance of each new wave stops (It has to). 


I think a better challenge; and one more in the "spirit" of the arcade, would be to start with six columns of invaders, and then add an additional column with each wave, until eleven columns are reached. Again, this is probably not possible due to technical limitations (...I wouldn't guess that I'm the only one who has thought of this, so it probably would have been done by now).


That being said, Thomas has once again shown his mastery of 6507 programming on the VCS platform. The row-by-row movement of the invaders is a perfect compromise between moving the entire "invading force" as a single unit (something that most Invaders ports do - including the original Atari VCS port and the 7800 home brew), or moving the individual "invaders" one-by-one (which, as I understand it, is why the invaders speed up as their numbers dwindle in the Arcade original).


I'm really looking forward to watching this game evolve. This view of the development process for these games is one of the most intriguing aspects of Atari Age. I thank all of the developers here for sharing this with us.

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