Rudy's Blog

No magic, just object reuse, object flicker, object duplicates/triplicates (via NUSIZx) and object shifting. Use Stella's Debug Colors (COMMAND-Comma on a Mac, ALT-Comma on Linux and Windows) to see what's going on.

The objects and what they're used for:

• player0 = left 3 cities
• player1 = right 3 cities, player's explosions (up to 3 via flicker)
• missile0 = incoming missiles, drawn in two groups (via flicker) where each group uses NUSIZ0 to show 1, 2 or 3 missiles OR 1 "fat" cruise missile (NUSIZ0 controls NUmber and SIZe of player0 and missile0 objects).
• missile1 = player's missile (moves from base to pointer)
• ball = player's pointer
• playfield = player's base, cliffs on left and right edge of screen, reserve missile indicators on left
• background = main screen color, then color changed for ground below cities.

You'll also notice the HMOVE "comb" that appears along the left edge of the screen. This is how the missiles are shifted left/right as they move down the screen.

I can't attach images to blog comments. If you use the Search feature in the forums, along with the words stella debug color, you'll find a number of examples that show and explain how games have been created using the limited objects of the Atari.

Cool, thanks!

Much of the challenge in programming the 2600 is figuring out how to create a particular game using the limited resources of the 2600. (Or vice-versa, coming up a game to build around interesting uses of the resources.) However, with bB some of that work has been done through it's preset kernels. (Unfortunately, that does mean that some games can't be done in bB because there's no matching kernel.)

I didn't know some games were impossible in bb. I'm not at a point yet where it probably makes a difference.

I didn't know some games were impossible in bb. I'm not at a point yet where it probably makes a difference.

 

It's not that some games are impossible in bB. it's just that you need to be ever more unconventional. Also, you might need to make your own mini-kernel or use inline assembly.

 

I've managed some smooth horizontal scrolling and even 4-way scrolling in bB.

 

RRatRace2.bin

 

project26.bin

Impressive. I was wondering about what you said before, is the limitations on sprites why in some games, like Spider Fighter, you can only have three or four missiles in play at a time? And if so, how did they draw all the spiders? I know, sprite multiplication. But it's so well done I never would have thought a system of two players, a ball, and two missiles could create it.

Think of the 2 sprites, 2 missiles and ball as crayons. You're actually telling the VCS when to drag each of those crayons across the screen. By expertly deciding when to use what crayon you can pretend like there's more sprites, laser blasts, etc..

 

This is also the advantage and disadvantage of batari BASIC. bB decides how you drag those "crayons" across the screen. You can still find ways to bend the rules but you do not have exact control like assembly.

 

For instance, in my game M.M.S.B.C. II I appear to have 2 player ships with their own laser blasts and up to 8 simulated enemies on screen - all with parallax scrolling.

mmsbcII.bin

This is way over my head. All I did last week was make two sprites and I couldn't even get that right lol.

This is way over my head. All I did last week was make two sprites and I couldn't even get that right lol.

 

Sorry about the poor explanation. My main point is that you can do more than you think in batari BASIC. With assembly you control every detail for maximum freedom. With batari BASIC you work within what it can do to find clever ways of getting what you want.

 

Also, check this video out:

Thanks, I'll watch that as soon as I can find my headphones.

This guy is a lot smarter than I am.

This guy is a lot smarter than I am.

 

He's a lot smarter than me for sure! What I'd take out of this video is how the 2600 works for games. The big secret is that he didn't have this awesome idea for Pitfall! He dinked around with what he found he could do and made a game from it

Well I was about halfway through this and then I had to do something and now I can't get it to play from where I stopped so I guess I'll have to watch the whole thing again from the beginning tomorrow, but thanks for showing it to me it's very interesting to hear these programmers discuss their work.

It's not that some games are impossible in bB. it's just that you need to be ever more unconventional. Also, you might need to make your own mini-kernel or use inline assembly.

IMHO that removes one of the main advantages of bB - not having to learn 6502. And if you're coding your kernel in ASM, you might as well go all the way and do everything in ASM.