Re: [stella] Stella Programmer's Guide Overhaul Project

Subject: Re: [stella] Stella Programmer's Guide Overhaul Project
From: Scott Huggins <sub17_5k@xxxxxxxxx>
Date: Thu, 18 May 2000 06:56:48 -0700 (PDT)
See, simple explanations like this might be a good
Appendix in the "Book" or Document.  It'd be really
neat to have simple explanations like Erik has
mentioned below of the most interesting "tricks" in
VCS games.

--- Erik Mooney <emooney@xxxxxxxxxxxxxxxx> wrote:
> >In Fast Food, how did they make the letters for
> You're
> >getting fatter?  Those ain't playfield graphics.
> 
> A 48-pixel-wide sprite.  Same thing as the six-digit
> score routine,
> except using static graphics instead of dynamic
> digits, and more height.
> 
> >In Space Invaders, how do they do it?  I'm guessing
> >the invaders are drawn with player graphics, but
> how
> >do they move the rows over?  Also, if I hold reset
> >while turning on the power =:-D I get two missiles,
> >and the invaders get two missiles, and they all
> move
> >independantly.  Where did it come from?
> 
> The invaders are player graphics, of course.  How
> they move the rows
> over is just to hit RESP0 and RESP1 at different
> times.  As for the
> lots-o-missiles... all the missiles are actually the
> ball.  The invaders
> get two missiles, both drawn with the ball (since
> they're separated
> vertically), and you get two missiles also separated
> vertically.  Your
> missiles and the invader missiles are each drawn on
> alternate frames,
> causing flicker.
> 
> >In Missile Command, how do they draw all the
> missiles
> >and their trails?  My only guess is with ball
> >graphics, but I can't see how--I thought you were
> >limited to one ball on screen at a time.  Likewise,
> >Pitfall with its swinging rope.  It changes color
> >depending on the scan line, so I'm guessing ball
> >again, but how?
> 
> Missile Command's missiles are one of the players,
> cloned if necessary.
> Two sets of missiles are drawn by flickering them on
> alternate frames.
> 
> >In "Asteroids", all those asteroids and the ship
> with
> >no flicker until you get over (I believe) 6
> asteroids
> >on screen.
> 
> No flicker?  Look again, bub.  They flicker as soon
> as you turn on the
> system.  Notice how all the upwards-moving asteroids
> move at the same
> rate, and so do all the downwards-moving ones?  The
> upwards ones are all
> drawn on one frame by reusing one player, and the
> downwards ones on
> alternate frames in the same way.
> 
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