Design Atari Player Missile Graphics
This Atari Basic Program demonstrates how to position a Player Missile Graphics character on the screen. This type of character is independent of the background characters on the screen. It can be moved in both horizontal or vertical positions.
This program sets a place in memory to store the Player Missile Graphics (setting it below RAMTOP memory). First we had to clear that memory area in line 50. Then it is draw (byte by byte) in line 70.
Initializing the Program
Line 10 colors the screen black with SETCOLOR 2,0,0. Then we create variables for the X (X1) and Y (Y1) positions.
Set Memory for Player Missile Graphic
The memory puts the Player Missile Graphics in memory below RAMTOP using line 20.
Line 30 sets the Player Missile Graphics character to 2 line resolution.
Set Position X, clear Y data, and Color it
Line 40 places the character at a horizontal position on the screen using the X register defined earlier.
Then the Player Missile Graphics is cleared with line 50 and it’s color is set.
Moving the Player Missile Graphic
Line 100 sets up the joystick control for our Player Missile Graphics character. If the joystick has a value of 15 that means no movement is taking place and we wait until the joystick controller is moved.
Suddenly the character begins movement as seen in the patterns below.
Line 100 initializes the joystick controller
Checking for the STICK value of A equal to 15 means that no movement has taken place yet.
A=11 – means it moved Left
A=7 – means it moved Right
A=13 – means it moved Up
A=14 – means it moved down
Finally we present the code and a screenshot of the Player Missile Graphics displayed on the screen with a black background.