atari2600land's Blog

I've toyed somewhat with the idea of Zoop. I think Batari Basic can probably be ruled out, since there's no way to get the playfield colors which are such an essential part of the game. I've only seen the demo, where the player is in the center and things come from the sides. Although that might be possible, it would work better to limit the player to shooting vertically so that the ship wouldn't have to share scan lines with the colored bricks.

 

With those restrictions in mind, it may be possible to implement a workable Zoop-style game using a custom kernel. Memory would be a little tight, but probably not unworkable.

How about instead of using the playfield blocks, using player1 to look like a block? There can be a whole bunch of copies of player1 on the same screen, as the Space Invaders demo made with bBasic proved. Or would that be a case of no matter how many different colors you use, the flicker would be too horrible? BTW, where is this demo you're talking about at?

How about instead of using the playfield blocks, using player1 to look like a block? There can be a whole bunch of copies of player1 on the same screen, as the Space Invaders demo made with bBasic proved. Or would that be a case of no matter how many different colors you use, the flicker would be too horrible? BTW, where is this demo you're talking about at?

 

Zoop basically requires the ability to have many differently-colored objects on a scan line at once. There are three ways this can be accomplished, none of which is amenable to Batari Basic.

 

The first approach is to change color registers on the fly. This is the approach I devised in 1994 for what would become Strat-O-Gems. Wonderful approach if you only need six colored objects per scan line. Some aspects of the kernel are a little tricky, but even in 1994 as a 2600 novice I was able to work things out.

 

The second approach is to display different colors on different scan lines and/or at different times and hope they blur together. Ladybug does this, but it's not a wonderful approach. Basically, you get black, one flickery color, another flickery color, or a less-flickery sum of the two colors.

 

The third approach is to overlay magnified sprites and the playfield. In and of itself, that doesn't provide a whole lot of colors, but it greatly improves the effectiveness of the second approach.

 

Here's a rough demo of combining the second and third approaches: http://www.atariage.com/forums/index.php?showtopic=70712

 

A key issue to be considered is that you need someplace to store all your 'pixels'. That paint demo uses 3/4 the 2600's memory to hold that picture. The 2600 has 1,024 bits of RAM, and every 7-color object (the minimum needed for Zoop) will require 3 bits to store it. I think you can see where Zoop could be quite a challenge.