Don't go!

Copyright © 2017 by Víctor Parada

This is a little game for the 2017 NOMAM's BASIC 10-liners Contest. This program fits in the PUR-80 category, and it was written using TurboBASIC XL 1.5 for the 8-bits ATARI XL/XE. Development started on 2017-02-04, and it took 2+2 days. The final version's date is 2017-02-26.

UPDATE: It obtained the 6th place of 26 entries in the category.

Description

With a paddle controller, try to keep the ball within the screen as much as you can.

Instructions

	Connect your paddles in port 1 and press the trigger on the working paddle to start.
	The ball will start moving slowly to one of the corners. Use this time to get used to your surrounding pads. All of them move at the same time, half of them in the opposite direction.
	When the ball hits a pad, it will bounce with a new random speed and angle, and the bounce's counter will be increased.
	Follow the ball or try to predict where it will go and put a pad there.
	If the ball goes out of the screen, the game is over. Your final score is the number of hits you did.

Development of the game

I like pong style games. I used to play Video Olympics, Warlords and Breakout in my old 2600. All of them have one thing in common: paddle controllers. Once, I thought about a self pong game, where one could play against himself. Yes, I was borred and found somehow difficult to handle two paddle controllers at the same time. If one paddle controlled both sides of a pong game, instead of left vs right hand, the points should be the number of bounces. It's name could be Selfpong.

With that old idea in my mind, I figured out a program for NOMAM contest. In the process, another idea came into my mind: what if instead of walls, I also add pads in the top and the bottom of the screen? Now, it could be named Quadrapong or something like that.

But I immediatelly noticed a problem: If all pads moves clockwise or counterclockwise at the same time, the corners would be weak points. The solution would be simple: to move horizontal and vertical pads to the corner at the same time. That introduced another degree of difficulty or challenge, it could be like rub the tummy and pat the head at the same time.

Then I thought about some other challenges for the game, like some items that randomly appear in the playfield and change the ball direction or speed, just to let the ball movement be less predictable and increase the difficulty as the time goes. Another improvement could be multiballs. What a mess!

It was time to start a prototype. I decided to program using TurboBASIC XL with P/M graphics and the collision detection registers. I also decided that single line resolution would be used, in order to add details to the ball. But needed 4 pads and a ball for the most simple prototype, so I had to decide which players and which missiles would be used for each element.

The first working prototype was done with P0 as the ball, P1 and P2 as the side pads, and 2 missiles as the top and bottom pads, but even in quad width, I found they were two small, so I used two missiles for each pad. The following is a screenshot with trace data in it:

1st prototype of the game

2nd fine-tunned prototype

As it could be seen, top and bottom pads have two colors, and that is not good, because it would limit the screen colors. But the game was playable and somehow difficult. It was during the tests of the gameplay when the final name of the game was taken.

I noticed some issues with collisions and that would make a bit harder to program the playfiled items. I felt frustrated on that and almost quit this project, but then I noticed that it has few shorth lines. If I add sounds and score, it might fit the PUR-80 category of NOMAM contest.

Well... I did it. But I changed some things. First, to solve the colors issue, I changed which player and missile was assigned for each pad, and enabling the fifth player instead of missiles, I got another color: 4 for normal players and 1 for the missiles. Then reassigned the players: the new order is ball, upper pad, lower and right, and one missile for the left pad. I also reduced the playfield some pixels.

This game was developed using Altirra in PAL video mode, but edited externally using a text editor and a propietary perl script that packs the BASIC code to be ENTERed into TurboBASIC XL interpreter. It was tested on both PAL and NTSC real 800XL using a paddle controller. It took me a couple of hours to pack this program in 800 bytes without obfuscating it more than it actually is. Enjoy it!

Download and try

Get the DONTGO.ATR file and set it as drive 1 in a real Atari or emulator. Turn on the computer and the game should start after loading. A pair of paddles in port 1 are required, but only one is used.

NOTE: If you try it using Altirra, in the "Input" menu you must select "Mouse -> Paddle A" for port 1. Once the mouse is captured by Altirra when you click over the emulator's window if it is in autocapture mode, or when you press F12, you can click the left button as the trigger to start the game, and the pads are moved when you move the mouse to the left and to the right. Press the middle button of the mouse or F12 to force Altirra to release the mouse device.

The code

The abbreviated BASIC code is the following:

The full and expanded BASIC listing is:

graphics 8

graphics 17

m=adr("{binary data}")

move m+9,704,8

poke 559,62

dim d(1)
d(0)=1
d(1)=-1

poke $D407,$A0

poke $D01D,3

poke $A8F0,3
move $A8F0,$A8F1,31

move m,$A520,4
move m,$A6D0,4

move m+17,$AAF0,9

dpoke $D003,$30C8

move m+4,$D008,5

poke 623,17

move m+26,$BE4E,9

while 1

  while ptrig(0)
  wend

  ? #6;"{cls}"

  s=0

  v=d(rand(2))
  w=d(rand(2))

  x=130
  y=112

  repeat

    poke 77,0

    x=x+v
    y=y+w

    if t
      s=s+t
      t=0
      position 9,23
      ? #6;s
    endif

    p=paddle(0)
    if p<50
      p=50
    endif
    if p>190
      p=190
    endif

    move $A8FE-p,$A300,256

    move $A80E+p,$A700,256

    sound

    poke $D001,p

    poke $D002,240-p

    pause 0

    poke $D000,x

    move $AB00-y,$A400,256

    poke $D01E,0
    pause 1

    if peek($D008) or peek($D00C)&8

      v=(rand(4)+2)*d(x>128)
      w=(rand(4)+2)*sgn(w)

      sound 0,30,8,8

      t=t+1
    endif

    if peek($D00C)&6

      sound 1,40,8,8

      t=t+1

      w=(rand(4)+2)*d(y>128)
      v=(rand(4)+2)*sgn(v)
    endif

  until x<9 or x>246 or y<10 or y>262

  sound 0,98,12,15
  pause 30
  sound

wend

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