C02/vcs/colorscr.c02

/* Atari VCS Color Bars Program */

#pragma origin $F800    //4k Cartridge
#include <vcshead.h02>  //TIA and RIOT Registers
#include <vcsstub.h02>  //Initialize VCS
#include <vcslib.h02>   //VCS Library Routines
#include <score2.h02>   //Two Player Score Kernel

zeropage char clrbkg; //Background Color
zeropage char clrmov; //Color Movement Flag
zeropage char clrofs; //Color Offset
zeropage char clrmsk; //Color/B&W Mask
zeropage char cntdwn; //Timer Countdown

char colors = {$86, $C6, $46, $00, $0E, $06, $0A, $00}; //Color Table

/* Setup Code */
void setup() {
}

/* Vertical Blank Code */
void vrtblk() {
  setclr(&colors); //Set Color Table
  scrprp(); //Prepare Score for Display
}

/* Execute Kernel Code */
void kernel() {
  CTRLPF = 2; //Set Score Mode 
  scrdsp(); //Display Scores (12 Scanlines)

  X=180; //Draw 180 Scanlines
  do {
    clrbkg = X;
    if (!SWCHB & 128) clrbkg<<;
    A = clrbkg + clrofs & clrmsk; //Set Background Color
    WSYNC = A;  //Wait for end of Scanline
    COLUBK = A; //Set Background Color
    X--;
  } while (X);
  return;
}

/* Execute Overscan Code */
void ovrscn() {
  if (!SWCHB & 1)  //Game Reset
    clrmov = $FF; //Turn On Scrolling
  if (!SWCHB & 2)  //Game Select
    clrmov = 0;   //Turn Off Scrolling
  clrmsk = (SWCHB & 8) ? $FF : $0F;
  if (clrmov) {
      if (SWCHB & 64) clrofs--; else clrofs++;  
  }
  cntdwn++;
  if (cntdwn == 10) {
    cntdwn = 0;      
    addbcd(1,&score2); //Increment Player 2 Score
    if (!score2) addbcd(1, &score1); //Increment Player 1 Score
  }  
}

#include <digits.h02>   //Digit Graphics
#include <vcsfoot.h02>  //Finalization Code