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5200 Programming Part 2


Tempest

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I've seen that done before, if you look at Centipede after the start up screen is displayed it blinks once and the rainbow patter stops while the word Centipede scrolls off the screen. For the longest time I wondered what caused that but now I realise that all they did was make a screen that looks exactly like the start up screen and then do that title movement thing. Pretty tricky, I wonder why they took the time to do that? I suppose you could do the same thing and change the date (slowly increment it to the right date). Maybe sometime after I get the main program done.

 

Does the joystick reading routine work the same way it does on Stella? Do I just read a register and roll the bits until I find the ones I want to look at? I as because the 5200 has the keypad and start, select, reset buttons which are going to make it a little more interesting.

 

Tempest

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I'm not sure yet, myself. My next goal is to alter the vertical movement of my player,then I'll move on to Joystik control. on the Atari 8-bits, you checked the value of stuff such as "strig(0)", etc. if it read some weird value like 11, for example, it was a press UP on the stick. I know I read all that stuff about the 5200, but I don't have my folder right now.

What would be great is if we could start saving parts of our code as little includes/subroutines, such as one which read the joystick values and changed the position of a character in screen RAM.

 

I have a question, and I'll use Joust to illustrate it.

 

1. The stone clouds in Joust are probably bg graphics, right? Draw bit by bit across the screen from top to bottom?

 

2. So then, are the ostrich , stork, pterries,and buzzards all players? How in the world are so many sprites able to be put on-screen at once, in a nutshell? I mean, sometimes they blink a bit, but only when the screen is very full.

 

3. Are eggs considered players too, or missiles? Guess , I know you guys never programmed this game.

 

I guess what I'm trying to gather is a series of methods one could use to get all those sprites on screen, since there are only a limited number of players and missiles the 5200/8bit hardware actually knows about.

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Hmm... I'd guess that the eggs are missiles since they're small and undetailed and coudl easily be done that way. The other characters I'm no so sure about. I suppose the 400/800 must have something like the 2600 where you can make multiple copies of a player and that's what I'm guessing they did. Just a guess though.

 

Take a look at this:

http://www.atarihq.com/reviews/atari8/comp...mputer_war.html

 

See the grid in the upper left? That's what I want to reproduce in my game. What do you suppose they did that in? Since it has a thin boarder I'm guessing it was all done in mode 8. My game will look somethinglike this (minus the map) but the grid will be much much larger and there will be more stuff to do (otherwise it would be pretty boring wouldn't it?).

 

Tempest

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As far as the boring part, I'm not concerned with that yet. I'm trying to just get the technical skills for now. once I feel more confident, I'll start my real first game.

 

I have a number of ideas I'm throwing around, but right now all are too ambitious for me to accomplish.

 

One game idea I'm mulling over:

 

Did you read the recent Crichton book, Timeline? Scientists travel in time to the middle ages, where (as in Jurassic Park) things are not exactly as we thought, much more dangerous with the extremely strong and huge knights and archers ...). Well, I thought about warping in and out of different times, trying to avoid arrows, running from fast knights on horseback, crossing rivers and bridges.

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I have tons of game ideas that I've put aside because there's no way I can program them yet. That's why I'm sticking to something simple with simple graphics.

 

BTW back to my other question, I think that grid had to be done with mdoe 8 graphics since part of the grid lines appear on every line and those must have been done in mode 8 (they're really thin). So unless they changed modes mid scan line about 16 times a line they must have just stuck with mode 8. This is going to make things a bit tougher.

 

Tempest

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No, I was talking about Graphics mode 8 (Antic mode F). You and Debro always talk in Antic numbers and I'm always talking in graphic numbers. It gets so confusing...

 

Anyway, Mode 8 gives you 320x160 resolution and 1 scan line per row. This makes for ultra fine detailed graphics but you only have 1 color so that can't be the way they did it in that game. They must have used the next lowest resoultion that allows more than one color and that would be mode 7 (Antic D) which gives you 160x96 resolution and 2 scan lines per row but allows up to 4 colors. This has to be what they did (and thus is what I shall do).

 

Tempest

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Oh yeah, when I used to program in Basic, I also referred to those Atari graphics modes, but now that I'm using ASM, it's too confusing for me to use both, so I just use the Antic mode number. Antic mode 8 = $48, Antic Mode 2 = $42, easy!

 

Another thing about your saying 'mode 8 graphics' was that I knew it only offered one color -- and that example is clearly NOT in that mode! I understand what you were saying now.

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