Pong, ball movement

[Retro Lord]

I'm having a bit of trouble with the ball movement in a pong game. I've set the ball movement up like this and it just gets stuck in the wall. There must be a better way?

 rem pushing the button starts the balls movement
 if a=0 && joy0fire then a=1
 rem ball going up and left
 if a=1 then ballx=ballx-1 : bally=bally-1
 rem ball going up and right
 if a=2 then ballx=ballx+1 : bally=bally-1

 rem ball going down and left
 if a=3 then ballx=ballx-1 : bally=bally+1
 rem ball going down and right
 if a=4 then ballx=ballx+1 : bally=bally+1

 if collision(ball,playfield) && a=1 then a=3
 if collision(ball,playfield) && a=2 then a=4
 if collision(ball,playfield) && a=3 then a=4
 if collision(ball,playfield) && a=4 then a=5

Entire code:

 set kernel_options no_blank_lines

 player1x=85
 player1y=80

 player0x=85
 player0y=70

 ballx=85 : bally=30



main

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


 player0:
        %11111111
        %00000000
        %00000000
        %00000000
        %00000000
        %00000000
        %00000000
        %00000000
end

 player1:
        %11111111
        %00000000
        %00000000
        %00000000
        %00000000
        %00000000
        %00000000
        %00000000
end


 COLUPF=$0E
 COLUP0=$0E
 COLUP1=$0E
 NUSIZ0=$30
 NUSIZ1=$30

   ballheight = 2 : rem * Ball 4 pixels high.

   CTRLPF = $21 : rem * Ball 4 pixels wide.


 drawscreen

 if a=0 && joy0fire then a=1
 rem ball going up and left
 if a=1 then ballx=ballx-1 : bally=bally-1
 rem ball going up and right
 if a=2 then ballx=ballx+1 : bally=bally-1

 rem ball going down and left
 if a=3 then ballx=ballx-1 : bally=bally+1
 rem ball going down and right
 if a=4 then ballx=ballx+1 : bally=bally+1

 if collision(ball,playfield) && a=1 then a=3
 if collision(ball,playfield) && a=2 then a=4
 if collision(ball,playfield) && a=3 then a=4
 if collision(ball,playfield) && a=4 then a=5




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

 if joy1left then player1x=player1x-1
 if joy1right then player1x=player1x+1

 goto main

[Retro Lord]

Got it working with the playfield now but it's a bit wonky when it comes to hitting the paddles, any pointers or ideas?

 if a=0 && joy0fire then a=1
 rem ball going up and left
 if a=1 then ballx=ballx-1 : bally=bally-1
 rem ball going up and right
 if a=2 then ballx=ballx+1 : bally=bally-1

 rem ball going down and left
 if a=3 then ballx=ballx-1 : bally=bally+1
 rem ball going down and right
 if a=4 then ballx=ballx+1 : bally=bally+1

 if bally=10 && a=1 then a=3
 if bally=10 && a=2 then a=4

 if ballx<20 && a=3 then a=4
 if ballx<20 && a=1 then a=2

 if ballx>120 && a=2 then a=1
 if ballx>120 && a=4 then a=3

 if collision(ball,player0) && a=3 then a=2
 if collision(ball,player0) && a=4 then a=1

[+Random Terrain]

Have you looked at this program:

 

atariage.com/forums/topic/211497-chipoff-breakout-style-example-program/

[Retro Lord]

I'll check it out

[Retro Lord]

Okay! That cleared a lot of things up for me, I got ball movement and hit detection up and running perfectly. But I have yet another question about scoring with 2 players.

 

I want 2 separate scores, one on the left side and one on the right side both starting at 0, and if respective player scores a point their score goes up. The only way I figured out how to do it is with sprite flicker and a counter, but that would take a little to much memory for my taste. Is there a better aproach to this?

[+Random Terrain]

See if this is helpful:

 

randomterrain.com/atari-2600-memories-batari-basic-commands.html#playerscores_minikernel

[Retro Lord]

Thank you, that minikernel was a lifesaver