Atari Basic: Game Tutorial

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(Intermediate) Here you will learn how to develop a simple game in Atari Basic. This game shows a square in the center screen that allows access to a piece of cheese. This display was created with GRAPHICS 3 which has no character display. What that means is all you will see are boxes when you use PLOT X,Y: DRAWTO X+XX, Y+YY and so on. GRAPHICS 2 however does allow the display of the regular Atari Basic characters which can be seen on the keyboard usually.

This video includes live audio where I explain stuff step by step of how this was done.

I am using a HP digital camera to record this so I can explain step by step what the program is doing. Since the Atari has no way to communicate with the PC audibly (without a special character) I decided to take this approach. Hopefully you will be able to see enough to follow through with my example.

In the past I noticed that my Atari videos were generated some type of audience (I think in the United Kingdom) and I can of abandoned them as they weren't getting a widespread amount of attention.

However recently I have gotten the urge to plunge into this again to see what people will think of this nice style of teaching.

I have my digital camera focused in range on my Dynex 37" LCD TV display. I have my Atari 800XL plugged into my Samsung DVD Recorder which is connected by an RCA jack to my TV. The plugs are connected to the video composite jacks on the back of the TV. Most Atari monitors in that day were built using similar connectors.

Please feel free to check out my other Atari Basic videos as well. I even have posted some Atari Machine Language programs in the past too. I am thinking about taking a closer look at the MAC/65 assembler programs since they are getting more views.

About me: I started on an Atari 65xe back in 1986. I learned to program in Basic through some books I purchased and also many countless trips to the library. In those days you could find a wide selection of Atari magazines and books. These days it would be rare to come across one, but they can be bought on ebay.

You can also either purchase your own Atari home computer on ebay or just use an Atari emulator. The emulators can be downloaded off the internet for free. An emulator allows your PC run programs that look very similar those found on the Atari computers back in the days. The emulator often will look different and may even run slow sometimes. Still though, an emulator cost you nothing and will save you the headache of finding a good Atari home computer.

About this program:
Program name: Mousetrap

Variables: X, Y, C, X1, Y1, J, COL

X,Y = represents where the little dot on the screen is located (horizontally and vertically)
C = indicates the color of the dot on the screen.
X1, Y1 = keeps track of where the dot previously was on the screen before it moved
J = keeps track of the movement locations of the joystick according to memory location 632
COL = used by LOCATE X,Y,COL to keep track of whether the dot has collided into another dot. This is known as a collision detector.

IF - this is known as a condition and waits for something to happen (joystick moving) before it executes the code following it.

COLOR values: (0 - 3)
0 = black (background color)
1 = orange
2 = green
3 = blue

COLORS can be changed with SETCOLOR 0,C,1 OR using POKES from 708-712

POKE 708, 100: (color register 0)
POKE 709,255 (color register 1)
POKE 710,50 (color register 2)
POKE 711,195 (color register 3)
POKE 712,15 (color register 4 - border)

C = 1: COLOR C:PLOT X,Y - draws a orange dot on the screen
COLOR 0:PLOT X,Y - erases the dot on the screen

Memory location 632:
J = PEEK(632)
When PRINT PEEK(632) is executed in Atari Basic the default value will be a 15 since the joystick has not yet moved.
When the joystick is moved to the right the value of J will be equal to 7 (player moved to the right)
When the joystick is moved to the left the value of J will be equal to 11 (player moved to the left)
When the joystick is moved up the value of J will be equal to 14 (player moved up)
When the joystick is moved down the value of J will be equal to 13 (player moved down)

TR = PEEK(644)
When the fire button is pressed TR=0 and TR=1 when released.

GOTO 30 - this allows the program to keep repeating in a loop. In the program example it goes back to the start of finding the joystick location and executes the code between lines 30 through 300 simultaneously until an action takes place (like the dot finding the cheese).

Please leave me comments about what you like or think the program can improve on.

Be sure to also check out:

https://sites.google.com/site/programmingtutorialsandmore/home

http://www.programmermind.com/atari/ataripage1.html

Website to demonstrate how the code works:
http://www.programmermind.com/AtariBasicGames1.html

Thank you for stopping by.