Crasher by Ted Szczypiorski

Crasher by Ted Szczypiorski

For Atari BASIC

Crasher is written in standard Atari 

BASIC. It utilizes custom characters to 

make the star field appear to scroll 

horizontally. It also uses 

Player/Missile graphics and technique 

to "print" the shapes to make them move 

a little smoother. It also uses a 

custom Display List.

Line 0:

Sets up protected memory for the custom 

character set and P/M graphics and sets 

variables for where they begin.

Displays WAIT message

Line 1:

sets up string variable storage. B$ has 

five spaces - used for erasing PM 

graphics. For loop is used to (a) copy 

character set; (b) clear some 

characters; (c) set up custom Display 

List.

Line 2:

Initializes A$, which stores the star 

field (a sequential string of 

characters). Clears the screen and 

switches to new character set. Sets 

up initial game play variables.

Line 3:

Pokes used to set up PM graphics. 

Initializes P$, which stores the ship 

data for the ship shapes (every 5 

characters is a different ship 

direction). Sets more variables.

Line 4:

This line resets the game variables 

(score, time, etc.). Changes screen 

color. Displays PRESS FIRE. Loops 

until button is pressed. Clears the 

top two lines (leaves stars in 

place). Resets screen to black.

Line 5:

This line resets the enemy ship. 

Changes sets new direction and x/y 

start.

Line 6:

This is the start of the game play 

loop. Decrements the timer. Displays 

time and score. Reads joystick and 

sets variables depending on joystick 

to move enemy ship accordingly.

Line 7:

Continues setting enemy ship 

variables. Determines direction of 

your ship. Updates character set for 

horizontal star scroll. Determines 

where a new line of stars (if any) 

should go for a vertical scroll.

Line 8:

Inserts or deletes a blank line for 

stars. Figures out string placement 

of enemy ship shape. Sets screen to 

Player 1 position and "prints" enemy 

ship with blanks above and below. 

Sets Screen to Player 0 position.

Line 9:

Prints player ship. Sets screen to 

actual screen. Sets random number 

used for stars and/or new ship. 

Prints new line of characters for 

stars, if need be. Updates counter 

for initial stars. Determines where 

to loop to: Line 6 for regular game 

loop. Line 5 for a new enemy ship. 

Line 4 for a new game. Line 7 for 

initial stars.