Simplest way of doing vertical scrolling?

[Rabbit 2600]

Experimenting on a racing game, and I want the playfield to scroll vertical. What would the simplest way of doing it be?

Also, I've been playing Gate Racer a lot and I really like the feature of having gates to go through, Any tips on how to achieve this feature? =)

 

Source:

  rem CODE INSPIRED BY Atarius Maximus at http://www.atariage.com/forums/index.php?showtopic=109288

TITLE

 drawscreen

 if joy0fire then goto start

 goto TITLE

start

  player0x = 50
  player0y = 80

 player1x = 255
 player1y = 255

 scorecolor = $0E

                                  dim _P1_L_R = player1x.a
                                  dim _P1_U_D = player1y.b
                                  dim _P0_L_R = player0x.c
                                  dim _P0_U_D = player0y.d

main


   AUDV0=0
   AUDV1=0

 a = a + 1

  rem POSSIBLY INEFFICIENT CODE, SEPARATE COLOR INFO FOR EACH FRAME...
        player0:
        %01000010
        %01111110
        %01011010
        %00011000
        %00111100
        %00111100
        %00111100
        %00111100
        %00100100
        %00100100
        %00111100
        %00011000
        %01011010
        %01111110
        %01011010
        %00011000
end

        player1:
        %01000010
        %01111110
        %01011010
        %00011000
        %00111100
        %00111100
        %00111100
        %00111100
        %00100100
        %00100100
        %00111100
        %00011000
        %01011010
        %01111110
        %01011010
        %00011000
end

 COLUP0 = $0E
 COLUPF = $0E
 COLUP1 = $0E

 playfield:
 ..X.X......................X.X..
 ..X.X......................X.X..
 ..X.X......................X.X..
 ..X.X......................X.X..
 ..X.X......................X.X..
 ..X.X......................X.X..
 ..X.X......................X.X..
 ..X.X......................X.X..
 ..X.X......................X.X..
 ..X.X......................X.X..
 ..X.X......................X.X..
end




EXPLOSION
  rem POSSIBLY INEFFICIENT CODE, SEPARATE COLOR INFO FOR EACH FRAME...
  if f = 10 then player1:
        %00110011
        %00110011
        %11001100
        %11001100
        %00110011
        %00110011
        %11001100
        %11001100
        %00110011
        %00110011
        %11001100
        %11001100
        %00110011
        %00110011
        %11001100
        %11001100
end

  if f = 20 then player1:
        %11001100
        %11001100
        %00110011
        %00110011
        %11001100
        %11001100
        %00110011
        %00110011
        %11001100
        %11001100
        %00110011
        %00110011
        %11001100
        %11001100
        %00110011
        %00110011
end

  if f=20 then f=0

  drawscreen

  if joy0right then player0x = player0x + 1
  if joy0left then player0x = player0x - 1

 if player1x < 15 then player1x = rand
 if player1x > 130 then player1x = rand

 if player1x = 255 then player1x = rand : player1y = 20

 if player1y > 90 then player1x = rand : player1y = 20 : e = (rand&3)

 if e = 0 then NUSIZ1 = $00
 if e = 1 then NUSIZ1 = $01
 if e = 2 then NUSIZ1 = $02
 if e = 3 then NUSIZ1 = $03

 _P1_U_D = _P1_U_D + 0.60

 if a = 60 then score = score + 1 : a = 0

 if joy0fire then goto faster

 goto main

faster

 _P1_U_D = _P1_U_D + 0.60

 if a = 30 then score = score + 1 : a = 0


  goto main

[+Random Terrain]

If you are using the standard kernel, there's a little example here:

 

http://www.randomterrain.com/atari-2600-memories-batari-basic-commands.html#pfscroll

[+Gemintronic]

The methods I've been posting for scrolling are not the simplest but allow you to have long levels by using DATA staements.

http://atariage.com/forums/topic/218357-vertical-scrolling-no-blank-lines-playercolors-demo/

http://atariage.com/forums/topic/218190-smooth-vertical-scrolling-from-data-want-4-way/

 

There is another method of just using a really long playfield statement

http://atariage.com/forums/topic/148427-vertical-scrolling-through-a-playfield-that-wont-fit-the-screen/?do=findComment&comment=1809236

 

So, those two options are if you want detailed levels. My suggestion is to play with R.T. links and do what you can with just pfscroll up and pfscroll down commands. All they do is cycle one screen up or down, though. You'll have to figure out how to make it look like a unqiue track/level even though it's just looping a single screen.

[bogax]

I think it would be interesting to have the track

generated on the fly with eg a pseudorandom

number generator, you wouldn't need all that

playfield data and the track could be really

long.

[+Gemintronic]

I think it would be interesting to have the track

generated on the fly with eg a pseudorandom

number generator, you wouldn't need all that

playfield data and the track could be really

long.

 

I'm being a total mooch here. I'd wish there was a function akin to wrev except instead of using a DATA statement it would call a PRNG. Something like

 

roomstyle = prnglevel( worldx, worldy, myseed)

 

My problem is that the built in random number generator didn't have a good enough distribution. Also, prnglevel(128, 64, myseed) should generate a different number than prnglevel(64, 128, myseed)