/* Atari VCS 2 Line Kernel Test` */

#pragma origin $F800    //4k Cartridge
#include <vcshead.h02>  //TIA and RIOT Registers
#include <vcsstub.h02>  //VCS Program Stub
#include <vcslib.h02>   //VCS Library Routines
#include <colors.h02>   //Color Selection Routines
#include <score2.h02>   //Two Player Score Kernel
#include <timerbar.h02> //Timer Bar Kernel
#include <arena.h02>    //Arena Two-Line Kernel

#pragma zeropage $80

//Boolean Equivalents
#define TRUE = $FF
#define FALSE = 0

//TIA Register Bit Masks
#define CLEAR = 0
#define SET = $0B

//Console Switch Bit Masks
#define P1DIFF = $80  //Player 1 Difficulty 
#define P0DIFF = $40  //Player 0 Difficulty
#define SELECT = $02  //Game Select
#define RESET  = $01  //Game Reset

//Joystick Direction Bit Masks
#define STK1UP = $01   //Joystick Up
#define STK1DN = $02   //Joystick Down
#define STK1LF = $04   //Joystick Left
#define STK1RT = $08   //Joystick Right
#define STK0UP = $10   //Joystick Up
#define STK0DN = $20   //Joystick Down
#define STK0LF = $40   //Joystick Left
#define STK0RT = $80   //Joystick Right


//Constants Required by arena.h02
#define ARLINS = 88     //88 Kernel Lines = 176 Scan Lines
#define ARMULT =  4     //Playfield Multiplier
#define P0LINS = 10     //Player 0 Lines
#define P1LINS = 10     //Player 1 Lines

zeropage char frame;  //Frame Counter
zeropage char cntdwn; //Countdown Timer
zeropage char arnclr; //Arena Playfield Color
zeropage char tmrclr; //Timer Playfield Color
zeropage char gstate; //Game State: #TRUE = Running
zeropage char clmask; //Color Cycling Mask

zeropage char p0xpos, p1xpos; //Player X-Positions
zeropage char p0ypos, p1ypos; //Player Y-Positions
zeropage char s0xpos, s1xpos; //Player Saved X-Positions
zeropage char s0ypos, s1ypos; //Player Saved Y-Positions

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

//Human Shaped Player Graphics
char human = {%00011100, %00011000, %00011000, %00011000, %01011010,
              %01011010, %00111100, %00000000, %00011000, %00011000};

//Aren Playfield Data
char arena0 = {$F0, $10, $10, $10, $10, $10, $10, $10, $10, $10, $10,
               $10, $10, $10, $10, $10, $10, $10, $10, $10, $10, $F0};

char arena1 = {$FF, $00, $00, $00, $00, $00, $0F, $08, $08, $08, $08,
               $08, $08, $08, $08, $0F, $00, $00, $00, $00, $00, $FF};

char arena2 = {$FF, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00,
               $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $FF};


/* Setup Code */
void setup() {
  gstate = #FALSE;
  init();
}

/* Initialize Game */
void init() {
  clmask = 0;
  frame = 0;
  cntdwn = 15;
  tmprep();        //Initialize Timer Bar
  p0xpos = 12;  p0ypos = 98;
  p1xpos = 136; p1ypos = 98;
}

/* Process Joystick */
void pstcks() {
  s0xpos = p0xpos; s0ypos = p0ypos;
  s1xpos = p1xpos; s1ypos = p1ypos;
  if (!SWCHA & #STK0UP) p0ypos++;
  if (!SWCHA & #STK0DN) p0ypos--;
  if (!SWCHA & #STK0RT) {p0xpos++; REFP0 = #CLEAR;}
  if (!SWCHA & #STK0LF) {
    if (p0xpos) {p0xpos--; REFP0 = #SET;}
  }
  if (!SWCHA & #STK1UP) p1ypos++;
  if (!SWCHA & #STK1DN) p1ypos--;
  if (!SWCHA & #STK1RT) {p1xpos++; REFP1 = #CLEAR;}
  if (!SWCHA & #STK1LF) {
    if (p1xpos) {p1xpos--; REFP1 = #SET;}
  }
}

/* Process Collisions */
void pclsns() {
  if (CXP0FB:-) {p0xpos = s0xpos; p0ypos = s0ypos;}
  if (CXP1FB:-) {p1xpos = s1xpos; p1ypos = s1ypos;}
  CXCLR = A;
}

/* Process Console Switches */
void pswchs() {
  if (!SWCHB & #SELECT) {
    setup();
  }
  if (!SWCHB & #RESET) {
    gstate = #TRUE;
    init(); 
  }
}
/* Vertical Blank Code */
void vrtblk() {
  pswchs();     //Process Console Switches
  setclr(clmask, &colors);  //Set Color Table
  tmrclr = getclr(clmask, $64, $04);
  arnclr = getclr(clmask, $46, $0A);
  scprep();                 //Prepare Score For Display
  posobj(p0xpos,0);         //Set P0 X-Position
  p0prep(p0ypos, &human);   //Set P0 Y-Position & Graphics Pointer
  posobj(p1xpos,1);         //Set P1 X-Position
  p1prep(p1ypos, &human);   //Set P1 Y-Position & Graphics Pointer
}

/* Execute Kernel Code */
void kernel() {	
  scdisp();     //Display Scores
  tmdisp(tmrclr);     //Display Timer Bar
  ardisp(arnclr);  //Display Playfield and Objects
}

/* Execute Overscan Code */
void ovrscn() {
  frame++;
  if (gstate) {
    if (!frame & 63) { //Decrement Timer Every X Frames
      if (!tmtick()) tmprep(); //Reset Timer if It Runs Out
    }
    pclsns(); //Process Collisions
    pstcks(); //Process Joysticks
  }
  else {
    if (!frame & 63) {
      if (cntdwn) cntdwn--;  //Countdown    
      else clmask++;  //Cycle Color Mask    
    }
  }
}

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