Couple of design questions....

[82-T/A]

Hey guys,

 

 

I'm really getting into this whole 2600 programming thing. I'm still mostly clueless how to program in Assembly, but I figured that in the mean time (in between lessons and such) I could narrow down the plan for my game.

 

I have a very specific type of game in mind that I'd like to develop. I have a couple of questions though...

 

 

1 - What is the standard 2600 resolution? And are there multiple resolutions?

 

2 - With question #1 in mind, is there a way that I can have relatively smaller font sizes on the screen? In one of the screens, I'd like to have somewhat of a shop type environment where a person can buy items. I might be totally overestimating the capabilities of the system when I say "screens". I plan to have say... a very basic intro screen (that doubles as a menu), a playing field screen, a hi-score screen, and maybe 1 or 2 other very basic screens (though interactive). The only part of the system that will at all be graphic intensive would be the playing field screen (which will be similar to StreetRacer). Does this sound like something that's possible?

 

3 - With what I've explained in #2, is there anything anyone can tell me, or perhaps some examples of games that function either as 4k, 8k, or 16k games? What kind of game is Solaris? I'm assuming that's a 16k game considering it's pretty decent graphics.

 

4 - I know the Atari 2600 lacks any kind of save-game feature. So what I thought I would do is create an option of the user of the game to be able to enter in a code to start at the same level he was at previously. I might either look for some type of encryption code, or something. This is something I can easily figure out the logic for in something like Delphi or Visual basic... but does this sound easily possible in Assembly? Do any other games currently use something like that?

 

 

Thanks!!!

[Robert M]

 

1 - What is the standard 2600 resolution? And are there multiple resolutions?

 

The total horizontal resolution is 160 pixels, however, there are constraints. The playfield/background horizontal resolution is 40 blocks at 4 pixels each (4 x 40 = 160). The horizontal position of the PF pixels is fixed, so there are be problem producing horizontal scrolls at low speeds. It looks jittery (See Super Cobra as an example of this phenomena)

 

Sprites are 8 pixels wide. The pixels of a sprite can be single, double, or quadruple wide. Sprites can be positioned horizontally to begin at any of the 160 possible positions. Missles are a single pixel 1, 2, 4, or 8 wide starting at any of the 160 possble positions.

 

Vertical resolution is 192 lines for NTSC. Some more for PAL. The vertical blockyness of all graphics is a function of your kernel code. For example, Combat has a vertical resolution on the tank sprites of 2 scanlines. the PF blocks have a vertical size of 8 scanlines (I think). Single scanline graphics are possible, but not much can be going on at the same time (see Atlantis) in any horizontal band on the screen. Check out in Atlantis how there is never more than 2 sprite objects in any horizontal band of the game screen. That is not by accident, but by design.

 

2 - With question #1 in mind, is there a way that I can have relatively smaller font sizes on the screen? In one of the screens, I'd like to have somewhat of a shop type environment where a person can buy items. I might be totally overestimating the capabilities of the system when I say "screens". I plan to have say... a very basic intro screen (that doubles as a menu), a playing field screen, a hi-score screen, and maybe 1 or 2 other very basic screens (though interactive). The only part of the system that will at all be graphic intensive would be the playing field screen (which will be similar to StreetRacer). Does this sound like something that's possible?

 

There are soem standard ways to show text on the VCS. You can use just PF graphics which gives you 40 pixels / 4 per character giving you 10 characters across.

-OR-

You can use a 6-digit scoring trick to generate a 48 pixel wide block which can show 48/4 = 12 characters at low res 3x5 or 3x7.

-OR-

You can use a flickering technique like in Stellar Track to generate 12 hi-res characters flickering at 30 Hz.

 

NOTE: Paul enhanced the second method to show 13 lo-res characters in his Homestar Runner RPG project. I believe he was inspired by my demo on the Stella mailing list of a non-flickering 13 character display that used PF graphics to form the letters 3x5, and then used the missles, ball and sprites to superimpose lines between the characters which would otherwise be touching at their sides.

 

 

3 -  With what I've explained in #2, is there anything anyone can tell me, or perhaps some examples of games that function either as 4k, 8k, or 16k games? What kind of game is Solaris? I'm assuming that's a 16k game considering it's pretty decent graphics.

 

There are many games that use bankswitching to get around the 4K limit of the original hardware. Search for Stella bankswitching on Google to find some stuff about it. The F8 switching scheme is probably the most common and AA has boards that use it.

 

4 - I know the Atari 2600 lacks any kind of save-game feature. So what I thought I would do is create an option of the user of the game to be able to enter in a code to start at the same level he was at previously. I might either look for some type of encryption code, or something. This is something I can easily figure out the logic for in something like Delphi or Visual basic... but does this sound easily possible in Assembly? Do any other games currently use something like that?

 

At some point all code is equivalent to Assembly language. The trick with the VCS is the small amount of RAM available. So any algorithm you design will need to take that limitation into account.

 

I believe the only game in existance to use a save game code is Secret Quest.

 

Thanks!!!

 

No problem. I will be posting lesson 12 some time this weekend.