General Information #

Author: Chris Page
Language: ACTION!
Compiler/Interpreter: ACTION!
Published: Analog #38 (01/ 86)

Air Hockey#

Air Hockey is written in Action! and must be compiled off of a disk or tape (the source and object code won't fit in memory together). So type it in. SAVE it, clear the editor, go to the monitor and RUN it, thusly: R "FILENAME“ (substituting the device and filename you saved it under for “FILENAME" — I used “D:AIRHOCKE.Y”).

Once you have it running properly, you should see the title screen and hear the title music (the “Peter Gunn" bass line). Press START.

Now you should see the options screen (it has the word OPTIONS at the top). You can use the OPTION key to highlight a different option. SELECT to change the option and START to play the game.

The options available in Air Hockey are:

Friction — This can be ON or OFF. If the friction is on, the puck will have a tendency to slow down while travelling across the board. You may notice that it sometimes curves as it slows down. This is because I used integer values instead of floating point. This means that the motion is not 100 percent accurate, resulting in the curved motion of the puck.

Velocity — This can be 2 through 9 and indicates the maximum velocity of the puck. Option 2 is slowest; 9 is fastest.

Bounce — This can be 0 through 9, indicating the amount of “bounce" to the puck, or how well it retains velocity after hitting the side of the board. A 9 means that the puck will not slow down on collision; 0 indicates very little bounce and will cause the puck to slow down considerably if it hits the sides.

Win — This is the score up to which the player(s) will play. It can be from 10 to 90, in increments of 10.

Players — Either 1 or 2. If one paver is selected, then the player should use joystick port 1 and control the top player; the computer will control player two, the bottom player. If two players are selected, then it's the same, except that player two will be controlled by joystick port 2.

Playing.#

Once your options are set (or left alone, if you like the default settings) you may press START to play. You'll then see a vertical air hockey board with the scores displayed at the top., along with the score necessary to win the game. T he puck will appear in front of the serving player's paddle. That player must hit the puck to start the game.

The game is something like Pong, with forward motion as well as side-to-side. Players control the paddles by moving the joystick in the direction they wish to move. The buttons do nothing. A score is made when the puck goes into the yellow goal area of a player, and the other player becomes the server.

If the puck gets stuck between players, as it can in real air hockey, you may re-serve by pressing the SPACE BAR. Also, while in the play mode, you may press the ESCape key to exit the program. Finally, if you want to restart the game. press START anytime during the game (except during the goal sequence), and you'll be returned to the options screen.

When the game is over, there's a long cheering sequence with whistling fans (if the crowd likes you) before you‘re returned to the title screen.

Why I did it or a tail of two ducks.#

I was sitting around one day (I do that quite a lot) last summer, had just bought Action! and was becoming familiar with it. After writing some demos, I was ready to do something more substantial with it.

I figured that a good way to utilize Action!‘s speed was to write some kind of fast-paced, arcade-type game. But I didn't want to write another space game or Pac-Man. I wanted to write something different and unique. Air Hockey may not be a completely unique game (it is similar to Pong). but it's different, and a change of pace from "Laser the Aliens"

A lesson in compromise or the quacker in the rye.#

This program is an example of inventiveness, procrastination and compromise. "Inventive” because. . .well, it's a matter of opinion. but I think it's inventive. “Procrastination" because I dropped the project for several months at a time (check out the start and completion dates in the source listing). Finally, and most decidedly, "compromise" because I made so many of these concerning Air Hockey.

Two of my main compromises were:

  1. I wanted more options and a complete title song, but time and a willingness to work (or the lack thereof) got in the way.
  2. Everyone, including myself, thought that the paddles should have been round. But that requires physics. . .I barely passed physics. If I'd made the paddles round, as they are in real life, I would have had to resort to "real" physics instead of the chintzy method I did use.
    In physics, you use vectors to describe how objects move, but this is a difficult thing in integers (well, difficult for me), which is what I was stuck with in Action! So I simply gave a horizontal and vertical speed and a horizontal and vertical direction.

These two compromises, however, were not as difficult or as important as my final compromise. I had to compromise on the one aspect, the most difficult thing, that every programmer must: completion of my goal. I had to stop work on a program which I felt was incomplete and short of my goals, and call it finished.

I realized this when I was telling my friends that I'd have to add the treble line to the title music before I'd submit it for publishing. As I told them this, I realized that the game is rather simple (as it was supposed to be) and that a full-blown song was superfluous. I than realized that other things I wanted to add were also not needed.

Actually. I had already met my goal (design a simple game as an exercise in Action!), but in the process, I'd created other goals—like adding the treble line.

I realized that I would continue creating goals as long as I was working on it; I would never finish the game. I'd sit, perma-bonded to my video screen, for the next ten years working on Air Hockey until it was 3-D, talked and had instant replay, a high score list, a theme song to put "Flight of the Valkyries" to shame, and a thousand other things... and I would still want to change something.

Program design and some ducks thrown in for effect.#

I think the important thing here is to realize that, when you want to write a program, you should decide exactly what it will be like, so that you can say it is finished when it meets the description. I certainly did not. l designed and wrote it as I went along (this is painfully evident to me in the lack of unity and consistency in the program, the "patchwork quilt" look).

This has also led to my big problem: because the program is so disorganized, I invariably come to some sort of dead end and drop the project. I completely gave up on Air Hockey many months back, but, at the urging of two of my friends (D.S. and D.B.), I picked it up again and trudged through the tangled code to finish it. . .finally. This is what has kept me from finishing the other hundred or so projects I have stored away in dusty disk files.

I'm sure that if it were not for this fact, there would be thousands more programs available for computers through other users, magazines and distributors. Next time you start to put something off because it seems too difficult, back up and try again.

Oh yes, the ducks.#

The ducks? Well, I thought I'd try to be a little different from the other articles gracing this magazine’s fine pages. (You wondered about them, didn’t you?) Have a duck., you'll feel better.
Chris Page is an eighteen-year-old from San Diego, who's studying for on A.A. degree in electronics at I.T.T. Technical Institute. He has worked with computers for seven years and owned on Atari 800 for four. His primary computing interests are in sound, graphics and human interfacing.
Listing 1
; ================
; =  Air Hockey  =
; =      by      =
; =  Chris Page  =
; ================

; Copyright (c) 1985 ANALOG Computing

; Special Thanks to:
; David Sullivan & David Becker

DEFINE
  OPTION="3",SELECT="5",START="6",
  NONE="7",LEFT="96",RIGHT="60",
  TOP="56",BOT="144"

BYTE
  NINDEX,VOLUME,FRICTION=[1],
  BOUNCE=[90],WIN=[10],PLAYERS=[2],
  HUE,LUM,OPT,PUCKXD,PUCKYD,HITFLAG,
  SERVER,GAMEOVER,SERVEIT,SDMCTL=559,
  CONSOL=53279,CHACT=755,WSYNC=54282,
  VCOUNT=54283,CRSINH=752,
  COLOR0=53270,COLOR1=53271,
  COLOR2=53272,COLOR3=53273,
  COLOR4=53274,RTCLOK=20,
  DMACTL=54272,LMARGN=82,RMARGN=83,
  CHBAS=756,PMBASE=54279,
  HITCLR=53278,P2PL=53262,
  GRACTL=53277,GPRIOR=623,
  RANDOM=53770,COLPM0=53266,
  COLPM1=53267,CH=764,RAMTOP=106,
  AUDCTL=53768,ATRACT=77,KEY

BYTE ARRAY
  DLIST,SCRMEM,RAMFONT,PMMEM($800),
  BAR(0)=[$FF$FF],
  PUCK(0)=[$60$F0$F0$F0$F0$F0$F0$60],
  TTOP(0)=['Q'R'R'R'R'R'R'S'S'S'S'R
           'R'R'R'R'R'E],
  TMID(0)=['R'T'T'T'T'T'T'T'T'T'T'T
           'T'T'T'T'T'R],
  TBOT(0)=['Z'R'R'R'R'R'R'S'S'S'S'R
           'R'R'R'R'R'C],
  NOTE(0)=[243 243 217 243 204 243
           193 204],
  YTOP(0)=[6 80],YBOT(0)=[62 144],
  SCORE(2),PDLX(2),PDLY(2),OSTIK(2),
  ROMSET($400)=$E000,HPOSP(4)=53248,
  HPOSM(4)=53252,PCOLR(4)=704

CARD
  PUCKXV,PUCKYV,PUCKX,PUCKY,
  MAXV=[500],DLISTL=560,SAVMSC=88,
  XITVBV=$E462


; --- Miscellaneous Procedures ---

PROC SETVBV=$E45C(BYTE CMD,VBIHI,
                  VBILO)


PROC VBI()
; VBI to play music
  SOUND(0,NOTE(NINDEX),10,VOLUME)
  SOUND(1,NOTE(NINDEX)-2,10,VOLUME)
  VOLUME==-1
  IF VOLUME=0 THEN
    VOLUME=15
    NINDEX==+1
    IF NINDEX=8 THEN
      NINDEX=0
    FI
  FI
; JMP XITVBV
  [$4C XITVBV]
RETURN


PROC INITVBI()
; Initialize music VBI
  NINDEX=0
  VOLUME=15
  SNDRST()
 ; set deferred vbi vector
  SETVBV(7,VBI RSH 8,VBI)
RETURN


PROC DEBOUNCE()
CARD I
; Debounce console keys
  FOR I=0 TO 5000 DO
    DO
      UNTIL CONSOL=NONE
    OD
  OD
RETURN


; --- Title Screen ---

PROC INITTITLE()
BYTE I
; Initialize title screen
  GRAPHICS(0)
  GPRIOR=17
  GRACTL=0
  SDMCTL=0
  CRSINH=1
  HUE=0
  DLIST=DLISTL
  DO
    UNTIL VCOUNT=0
  OD
  FOR I=3 TO 5 DO
    DLIST(I+7)=DLIST(I)
  OD
  SETBLOCK(DLIST,10,$70)
  FOR I=13 TO 25 STEP 2 DO
    DLIST(I)=0
  OD
  SETBLOCK(DLIST+27,2,$70)
  SETCOLOR(1,0,14)
  SETCOLOR(2,0,8)
  POSITION(11,0)
  PRINT("Air Hockey")
  POSITION(1,1)
  PRINT("By: Chris Page")
  POSITION(29,1)
  PRINT("Thanks: D.S. and D.B.")
  POSITION(17,2)
  PRINT(
   "June 30, 1984 - August 9, 1985")
  POSITION(7,4)
  PRINT("Copyright (c) 1984")
  POSITION(34,5)
  PRINT("Press  START")
  SDMCTL=33
RETURN


PROC TITLECOLORS()
BYTE I
; Mid-screen color changes
  HUE==+2
  IF HUE&2 THEN
    CHACT==+1&3
  FI
  FOR I=0 TO 30 DO
    DO
      WSYNC=0
      COLOR4=VCOUNT LSH 1+HUE
      IF VCOUNT=48 THEN
        COLOR1=0
      FI
      UNTIL VCOUNT&128
    OD
  OD
RETURN


PROC TITLE()
; Display title screen
  INITTITLE()
  INITVBI()
  DO
    TITLECOLORS()
    UNTIL CONSOL=START
  OD
  SDMCTL=0
RETURN


; --- Game Options ---

PROC INITOPTIONS()
; Initialize procedure OPTIONS()
  GRAPHICS(17)
  SDMCTL=0
  GRACTL=0
  DO
    UNTIL VCOUNT=0
  OD
  DEBOUNCE()
  SCRMEM=SAVMSC
  DLIST=DLISTL
  DLIST(3)==+1
  SETCOLOR(0,3,14)
  SETCOLOR(2,0,14)
  PRINTDE(6,"    GAME OPTIONS")
  POSITION(0,2)
  PRINTD(6,"OPTION - NEXT OPTION")
  PRINTDE(6,"SELECT - CHOOSE")
  PRINTDE(6," START - PLAY GAME")
  POSITION(3,6)
  PRINTD(6,"FRICTION: O")
  IF FRICTION THEN
    PRINTD(6,"N")
  ELSE
    PRINTD(6,"FF")
  FI
  POSITION(3,8)
  PRINTD(6,"VELOCITY: ")
  PRINTBD(6,MAXV/100)
  POSITION(3,10)
  PRINTD(6,"BOUNCE  : ")
  PRINTBD(6,BOUNCE/10)
  POSITION(3,12)
  PRINTD(6,"WIN AT  : ")
  PRINTBD(6,WIN)
  POSITION(3,14)
  PRINTD(6,"PLAYERS : ")
  PRINTBD(6,PLAYERS)
  SDMCTL=34
  OPT=0
RETURN


PROC OPTIONCOLORS(BYTE OPT)
; Mid-screen color changes
; OPT=option line to hi-light
  DO
    WSYNC=0
    UNTIL VCOUNT=15
  OD
  LUM=0
  WSYNC=0
  DO
    WSYNC=0
    COLOR0=LUM&$0F%$20
    LUM==+2
    UNTIL VCOUNT=25
  OD
  WSYNC=0
  COLOR0=0
  COLOR4=6
  DO
    WSYNC=0
    UNTIL VCOUNT=40
  OD
  COLOR0=$F8
  OPT==LSH 3+41
  DO
    WSYNC=0
    UNTIL VCOUNT=OPT
  OD
  COLOR0=$FE
  DO
    WSYNC=0
    UNTIL VCOUNT=OPT+8
  OD
  COLOR0=$F8
RETURN


PROC OPTIONS()
CARD I
; Get game options from player(s)
  INITOPTIONS()
  DO
    FOR I=0 TO 10 DO
      OPTIONCOLORS(OPT)
      UNTIL CONSOL=START
    OD
    IF CONSOL=OPTION THEN
      OPT==+1
      IF OPT=5 THEN
        OPT=0
      FI
    FI
    IF CONSOL=SELECT THEN
      IF OPT=0 THEN
        FRICTION==!1
        IF FRICTION THEN
          SCRMEM(134)=46
          SCRMEM(135)=0
        ELSE
          SCRMEM(134)=38
          SCRMEM(135)=38
        FI
      ELSEIF OPT=1 THEN
        IF MAXV=900 THEN
          SCRMEM(173)==-7
          MAXV=200
        ELSE
          SCRMEM(173)==+1
          MAXV==+100
        FI
      ELSEIF OPT=2 THEN
        IF BOUNCE=90 THEN
          SCRMEM(213)==-9
          BOUNCE=0
        ELSE
          SCRMEM(213)==+1
          BOUNCE==+10
        FI
      ELSEIF OPT=3 THEN
        IF WIN=90 THEN
          SCRMEM(253)==-8
          WIN=10
        ELSE
          SCRMEM(253)==+1
          WIN==+10
        FI
      ELSE
        IF PLAYERS=2 THEN
          SCRMEM(293)==-1
          PLAYERS=1
        ELSE
          SCRMEM(293)==+1
          PLAYERS=2
        FI
      FI
    FI
    UNTIL CONSOL=START
  OD
  SDMCTL=0
  SNDRST()
RETURN


; --- Play Air Hockey ---

PROC MAKEFONT()
BYTE I
CARD J
; Change character set

BYTE ARRAY
  CDAT(8)=[$55$55$55$55$54$54$50$40],
  EDAT(8)=[$40$50$54$54$55$55$55$55],
  QDAT(8)=[$01$05$15$15$55$55$55$55],
  RDAT(8)=[$55$55$55$55$55$55$55$55],
  SDAT(8)=[$FF$FF$FF$FF$FF$FF$FF$FF],
  TDAT(8)=[$AA$AA$2A$AA$AA$AA$A2$AA],
  ZDAT(8)=[$55$55$55$55$15$15$05$01]

  RAMFONT=(RAMTOP-8)*$100
  MOVEBLOCK(RAMFONT,ROMSET,$400)
  ZERO(RAMFONT+536,192)
  CHBAS=RAMTOP-8
  SDMCTL=61
  FOR I=0 TO 7 DO
    FOR J=0 TO 3000 DO OD
    RAMFONT(536+I)=CDAT(I)
    RAMFONT(552+I)=EDAT(I)
    RAMFONT(648+I)=QDAT(I)
    RAMFONT(656+I)=RDAT(I)
    RAMFONT(664+I)=SDAT(I)
    RAMFONT(672+I)=TDAT(I)
    RAMFONT(720+I)=ZDAT(I)
  OD
RETURN


PROC POSPLAYER(CARD PLAYER
               BYTE X,Y,LENGTH
               BYTE ARRAY SHAPE)
; Position Player
  HPOSP(PLAYER)=X+LEFT
  PLAYER==*$100+$400
  MOVEBLOCK(PMMEM+PLAYER+Y+TOP,
            SHAPE,LENGTH)
RETURN


PROC POSPDL(BYTE PADDLE,X,Y)
; Position paddle
  POSPLAYER(PADDLE,X,Y,2,BAR)
RETURN


PROC POSPUCK(CARD X,Y)
; Position puck
  X==/100
  Y==/100
  POSPLAYER(2,X,Y,8,PUCK)
RETURN


PROC ERASEPDL(CARD PADDLE  BYTE Y)
; Erase paddle
  PADDLE==*$100+$400
  ZERO(PMMEM+PADDLE+Y+TOP,2)
RETURN


PROC ERASEPUCK(CARD Y)
; Erase puck
  Y==/100+TOP
  ZERO(PMMEM+$600+Y,8)
RETURN


PROC ERASEALL()
; Clear Player memory
  ERASEPDL(0,PDLY(0))
  ERASEPDL(1,PDLY(1))
  ERASEPUCK(PUCKY)
RETURN


PROC INITPMG()
; Initialize PMG
  PMMEM=(RAMTOP-16)*$100
  Zero(PMMEM,$800)
  PCOLR(0)=$76
  PCOLR(1)=$76
  PCOLR(2)=$36
  PMBASE=RAMTOP-16
  GRACTL=3
RETURN


PROC INITPLAY()
CARD I
; Initialize game
  GRAPHICS(0)
  SDMCTL=0
  DO
    UNTIL VCOUNT=0
  OD
  SETVBV(7,$E4,$62)
  SNDRST()
  DEBOUNCE()
  INITPMG()
  SCRMEM=SAVMSC
  SCORE(0)=0
  SCORE(1)=0
  OSTIK(0)=15
  OSTIK(1)=15
  SERVER=0
  GAMEOVER=0
  CRSINH=1
  DLIST=DLISTL
  DLIST(2)=DLIST(3)+4
  DLIST(3)=DLIST(4)
  DLIST(4)=DLIST(5)
  DLIST(5)=$30
  DLIST(7)=$30
  SETBLOCK(DLIST+8,21,4)
  SETCOLOR(0,3,6)
  SETCOLOR(1,0,14)
  SETCOLOR(2,0,4)
  SETCOLOR(3,2,14)
  SETCOLOR(4,0,6)
  POSITION(3,0)
  PRINTE("air hockey")
  SAVMSC==+16
  POSITION(0,0)
  PRINTF(
   " One : 00 | Win : %B | Two : 00",
   win)
  MOVEBLOCK(SCRMEM+55,TTOP,18)
  FOR I=87 TO 663 STEP 32 DO
    MOVEBLOCK(SCRMEM+I,TMID,18)
  OD
  MOVEBLOCK(SCRMEM+695,TBOT,18)
  MAKEFONT()
  SOUND(3,0,0,3)
  KEY=0
  CH=$FF
RETURN


PROC SERVE(BYTE PLAYER)
CARD I
; Initialize positions
  ERASEALL()
  PDLX(0)=28
  PDLX(1)=28
  PDLY(0)=YTOP(0)
  PDLY(1)=YBOT(1)
  PUCKX=3000
  PUCKY=4000+6800*PLAYER
  PUCKXV=0
  PUCKYV=0
  POSPDL(0,PDLX(0),PDLY(0))
  POSPDL(1,PDLX(1),PDLY(1))
  POSPUCK(PUCKX,PUCKY)
  HITCLR=0
  HITFLAG=0
  VOLUME=0
RETURN


PROC MOVEPADDLE(BYTE P)
BYTE STIK
; Move paddle
  ERASEPDL(P,PDLY(P))
  STIK=STICK(P)
  ; move puck 2 for one player game
  IF PLAYERS=P THEN
    STIK=$F
    IF PDLX(1)+2<PUCKX/100 THEN
      STIK==-8
    ELSE
      STIK==-4
    FI
    IF PDLY(1)-6<PUCKY/100 THEN
      STIK==-2
    ELSEIF PDLY(1)-8>PUCKY/100 THEN
      STIK==-1
    ELSE
      STIK==-2
      IF RAND(2) THEN
        STIK==+1
      FI
    FI
  FI
  ; save stick position
  OSTIK(P)=STIK
  ; move paddle verticaly
  IF (STIK&1)=0 THEN
    PDLY(P)==-2
    IF PDLY(P)<YTOP(P) THEN
      PDLY(P)=YTOP(P)
    FI
  ELSEIF (STIK&2)=0 THEN
    PDLY(P)==+2
    IF PDLY(P)>YBOT(P) THEN
      PDLY(P)=YBOT(P)
    FI
  FI
  ; move paddle horizontaly
  IF (STIK&8)=0 THEN
    PDLX(P)==+2
    IF PDLX(P)>RIGHT-4 THEN
      PDLX(P)=RIGHT-4
    FI
  ELSEIF (STIK&4)=0 THEN
    PDLX(P)==-2
    IF PDLX(P)>240 THEN
      PDLX(P)=0
    FI
  FI
  POSPDL(P,PDLX(P),PDLY(P))
RETURN


PROC REVERSEPX()
; Reverse horizontal puck direction
  VOLUME=14
  PUCKXD==!1
  IF PUCKXV<(90-BOUNCE) THEN
    PUCKXV=0
  ELSE
    PUCKXV==-(90-BOUNCE)
  FI
RETURN


PROC REVERSEPY()
; Reverse vertical puck direction
  VOLUME=14
  PUCKYD==!1
  IF PUCKYV<(90-BOUNCE) THEN
    PUCKYV=0
  ELSE
    PUCKYV==-(90-BOUNCE)
  FI
RETURN


PROC MOVEPUCK()
BYTE PADDLE,XDIF,YDIF,STIK,ABOVE
CARD ARRAY
  XVELOC(0)=[400 140 100  80  40  0
              40  80 100 140 400]
; Move the puck
  ERASEPUCK(PUCKY)
; check for paddle collisions
  PADDLE=0
  IF PUCKY/100>70 THEN
    PADDLE=1
  FI
  STIK=OSTIK(PADDLE)
  IF P2PL THEN
    IF HITFLAG=0 THEN
      VOLUME=14
    ; new x velocity & direction
      XDIF=PUCKX/100+3-PDLX(PADDLE)
      PUCKXV=XVELOC(XDIF)
      PUCKXD=0
      IF XDIF>5 THEN
        PUCKXD=1
      FI
    ; new y velocity & direction
      YDIF=PUCKY/100-PDLY(PADDLE)
      ABOVE=0
      IF PADDLE THEN
        IF PUCKY/100<PDLY(1) THEN
          ABOVE=1
        FI
      ELSE
        IF PUCKY/100+8<PDLY(0) THEN
          ABOVE=1
        FI
      FI
    ; paddle not moving
      IF (STIK&3)=3 THEN
        PUCKYD==!1
    ; puck not moving
      ELSEIF PUCKYV=0 THEN
        PUCKYV=200
        PUCKYD=0
        IF (STIK&3)=1 THEN
          PUCKYD=1
        FI
    ; puck and paddle equal y coord
      ELSEIF PUCKY/100+3=PDLY(PADDLE)
       THEN
      ; do nothing
      ELSE
      ; moving puck and paddle down
        IF PUCKYD=1 AND (STIK&3)=1
         THEN
          IF ABOVE THEN
            PUCKYV==-200
            IF PUCKYV>200 THEN
              PUCKYD==!1
            FI
          ELSE
            PUCKYV==+200
          FI
        ELSEIF PUCKYD=0 AND
               (STIK&3)=2 THEN
          IF ABOVE=0 THEN
            PUCKYV==-200
            IF PUCKYV>200 THEN
              PUCKYD==!1
            FI
          ELSE
            PUCKYV==+200
          FI
        ELSEIF PUCKYD=1 AND
               (STIK&3)=2 THEN
          IF ABOVE THEN
            PUCKYD==!1
            PUCKYV==+200
          FI
        ELSEIF PUCKYD=0 AND
               (STIK&3)=1 THEN
          IF ABOVE=0 THEN
            PUCKYD==!1
            PUCKYV==+200
          FI
        FI
      FI
    FI
    HITFLAG=1
  ELSE
    HITFLAG=0
  FI
  HITCLR=0
; move horizontaly
  IF PUCKXV>MAXV THEN
    PUCKXV=MAXV
  FI
  IF PUCKXD THEN
    PUCKX==+PUCKXV
  ELSE
    PUCKX==-PUCKXV
  FI
; check boundaries
  IF PUCKX>24000 THEN
    REVERSEPX()
    PUCKX=0
  ELSEIF PUCKX>RIGHT*100 THEN
    REVERSEPX()
    PUCKX=RIGHT*100
  FI
  IF PUCKYV>MAXV THEN
    PUCKYV=MAXV
  FI
; move verticaly
  IF PUCKYD THEN
    PUCKY==+PUCKYV
  ELSE
    PUCKY==-PUCKYV
  FI
; check boundaries
  IF PUCKY>24000 THEN
    REVERSEPY()
    PUCKY=0
  ELSEIF PUCKY>BOT*100 THEN
    REVERSEPY()
    PUCKY=BOT*100
  FI
; handle friction
  IF PUCKXV THEN
    PUCKXV==-FRICTION
  FI
  IF PUCKYV THEN
    PUCKYV==-FRICTION
  FI
; fading collision sound
  IF VOLUME THEN
    VOLUME==-2
    SOUND(0,10,8,VOLUME)
    SOUND(1,10,10,VOLUME)
  ELSE
    SOUND(0,0,0,0)
    SOUND(1,0,0,0)
  FI
  POSPUCK(PUCKX,PUCKY)
RETURN


PROC GOAL(BYTE PLAYER)
BYTE I
CARD J
; Inc score, check for a winner
  SNDRST()
  ERASEPUCK(PUCKY)
  VOLUME=0
  SERVEIT=1
  SERVER=PLAYER
  SCORE(PLAYER)==+1
  IF SCORE(PLAYER)=WIN THEN
    GAMEOVER=1
  FI
; flash score
  FOR I=0 TO 5 DO
    SETBLOCK(SCRMEM+23+22*PLAYER,2,0)
    FOR J=0 TO 5000 DO OD
    SCRMEM(23+22*PLAYER)=
           16+SCORE(PLAYER)/10
    SCRMEM(24+22*PLAYER)=
           16+SCORE(PLAYER) MOD 10
    SOUND(0,20,10,8)
    FOR J=0 TO 5000 DO OD
    SOUND(0,0,0,0)
  OD
; cheering
  IF GAMEOVER=0 THEN
    FOR I=0 TO 30 DO
      FOR J=0 TO 1000 DO OD
      SOUND(0,10,8,I RSH 1)
    OD
    FOR J=0 TO 40000 DO OD
    FOR I=0 TO 30 DO
      FOR J=0 TO 1000 DO OD
      SOUND(0,10,8,15-I RSH 1)
    OD
  FI
  SNDRST()
  SOUND(3,0,0,3)
RETURN


PROC MOVEALL()
; Move paddles and puck
; keep attract mode at bay
  ATRACT=0
; check for goal
  IF PUCKX>2400 AND PUCKX<3700 THEN
    IF PUCKY=0 THEN
      GOAL(1)
    ELSEIF PUCKY=BOT*100 THEN
      GOAL(0)
    FI
  FI
  IF GAMEOVER=0 THEN
    MOVEPUCK()
    MOVEPADDLE(0)
    MOVEPADDLE(1)
  FI
RETURN


PROC ENDGAME()
BYTE I
CARD J,K
; Cheer profusly and end game
  SNDRST()
  FOR I=0 TO 30 DO
    FOR J=0 TO 1000 DO OD
    SOUND(0,10,8,I RSH 1)
  OD
  FOR J=0 TO 200 DO
    FOR K=0 TO 500 DO OD
    IF RAND(130)=0 THEN
      FOR I=0 TO 15 DO
        FOR K=0 TO 1200 DO OD
        SOUND(1,30-I,10,I)
      OD
      FOR I=0 TO 15 DO
        FOR K=0 TO 1200 DO OD
        SOUND(1,15+I,10,15-I)
      OD
    FI
  OD
  FOR I=0 TO 30 DO
    FOR J=0 TO 1000 DO OD
    SOUND(0,10,8,15-I RSH 1)
  OD
  FOR J=0 TO 40000 DO OD
RETURN


PROC PLAY()
; Play Air Hockey
  INITPLAY()
  SERVE(SERVER)
  DO
    DO
      UNTIL VCOUNT=100
    OD
    IF CH<>$FF THEN
      KEY=GETD(1)
    FI
    IF KEY=32 OR SERVEIT=1 THEN
      SERVE(SERVER)
      KEY=0
      CH=$FF
      SERVEIT=0
    FI
    MOVEALL()
    UNTIL GAMEOVER=1 OR KEY=27 OR
          CONSOL=6
  OD
  IF KEY<>27 AND CONSOL<>6 THEN
    ENDGAME()
  FI
  SNDRST()
RETURN


; --- Main Procedure ---

PROC MAIN()
  LMARGN=0
  CLOSE(1)
  OPEN(1,"K:",4,0)
  DO
    TITLE()
    WHILE CONSOL=6 DO
      OPTIONS()
      PLAY()
    OD
    UNTIL KEY=27
  OD
  CLOSE(1)
  GRAPHICS(0)
  GRACTL=0
RETURN

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