snake2100.c

int main()
{
  //saveregs();
  // uint oldD011 = peek( 0xD011 );
  //uint oldD016 = peek( 0xD016 );
  //uint oldD018 = peek( 0xD018 );
  uint oldD020 = peek( 0xD020 );
  uint oldD021 = peek( 0xD021 );
  uint oldChar = peek( 0x0286 );


  introScreen();

  uint i = NULL;
  word j = NULL;
  
  uint x1 = NULL;
  uint y1 = NULL;
  
  uint length = NULL;
  uint lastx = NULL;
  uint lasty = NULL;
  uint gameover = NULL;
  uint newx1 = NULL;
  uint c = NULL;
  word score = NULL;
  word r0 = NULL;
  
  uint newy1 = NULL;

  uint player = 81;
  uint trail = 87;

  word timer = 0x0000;
  word freq = NULL;
  
  poke( XYtoMEMLOC(), trail );

  //lda( 0x12 );
  //lda( 147 );
  // set printf colour to white
  lda( 0x05 );
  jsr( 0xFFD2 );

  uint keepplaying = 0x01;
  while( keepplaying == 1 )
    {
      resetVariables();
      screenSetup();
      c = getin();
      setcolours();
      while( gameover == 0 )
	{
	  if( timer == freq )
	    {
	      // vv checkUp 
	      if( c == 33 )
		{
		  if( y1 != 0 )
		    {
		      lastx = 0x00;
		      lasty = 0xFF;
		    }
		  else
		    {
		      lasty = 0x00;
		    }
		}

	      // ^^ checkUp
	      
	      // vv check Down
	      if( c == 37 )
		{
		  if( y1 != 24 )
		    {
		      lastx = 0x00;
		      lasty = 0x01;
		    }
		  else
		    {
		      lasty = 0x00;
		    }
		}


	      // ^^ check Down
	      
	      // vv check Left
	      if( c == 30 )
		{
		  if( x1 != 0 )
		    {
		      lastx = 0xFF;
		      lasty = 0x00;
		    }
		  else
		    {
		      lastx = 0x00;
		    }
		}
	      
	      // ^^ checkLeft
	      // vv checkRight
	      //checkRight();
	      if( c == 38 )
		{
		  if( x1 != 39 )
		    {
		      lastx = 0x01;
		      lasty = 0x00;
		    }
		  else
		    {
		      lastx = 0x00;
		    }
		}
	      // ^^ checkRight
	      timer = 0x0000;
	      c = getin();
	      // vv UpdatePosition
	      //updatePosition();
	      newx1 = x1 + lastx;
	      newy1 = y1 + lasty;  
	      if( newx1 == 0xFF )
		{
		  newx1 = 0x00;
		}
	      if( newx1 == 40 )
		{
		  newx1 = 39;
		}
	      if( newy1 == 0x01 )
		{
		  newy1 = 0x02;
		}
	      if( newy1 == 25 )
		{
		  newy1 = 24;
		}
	      poke( XYtoMEMLOC(), trail );

	      if( peek(NextXYtoMEMLOC()) == trail )
		{
		  if( newx1 != x1 )
		    {
		      gameover = 1;
		    }
		  if( newy1 != y1 )
		    {
		      gameover = 1;
		    }
		}
	      else
		{
		  score = score + 1;
		  //showScore();
		  cursorxy( 7, 0 );
		  printf( score );
		  if( freq > 0x0030 )
		    {
		      freq = freq - 3;
		    }
		}
	      x1=newx1;
	      y1=newy1;  
	      poke( XYtoMEMLOC(), player );

	      // ^^ updatePosition
	    }
	  inc(timer);
	  
	  if( c == 62 )
	    {
	      gameover = 1;
	      clearkb();
	    }
	}
      keepplaying = playAgain();
    }
  clearkb();
  //poke( 0xD011, oldD011 );
  //poke( 0xD016, oldD016 );
  //poke( 0xD018, oldD018 );
  poke( 0xD020, oldD020 );
  poke( 0xD021, oldD021 );
  poke( 0x0286, oldChar );

  return;
}

void resetVariables()
{
  x1 = 20;
  y1 = 12;
  freq = 0x04FF;
  length = 0x00;
  lastx = 0x00;
  lasty = 0x00;
  gameover = 0x00;
  newx1 = 0x00;
  newy1 = 0x00;
  score = 0x0000;
  return;
}

word XYtoMEMLOC()
{
  r0 = 1024 + x1 + y1 * 40;
  return r0;
}

word NextXYtoMEMLOC()
{
  r0 = 1024 + newx1 + newy1 * 40;
  return r0;
}




void screenSetup()
{
  cls();
  cursorxy( 0, 0 );
  printf( "SCORE:" );
  cursorxy( 11, 0 );
  printf( "MOVE:  UP:I  DN:K  LT:U  RT:O" );
  for( j = 1064; j < 1104; j = j + 1 )
    {
      poke( j, 67 );
    }
  return;
}

void introScreen()
{
  screen(0);
  cls();

  cursorxy( 2, 1 );
  printf( " SSSSS  N     N  AAAA  K    K EEEEEE" );
  cursorxy( 2, 2 );
  printf( "SS   SS NN    N A    A K  K   E" );
  cursorxy( 2, 3 );
  printf( "SS      N N   N A    A KK     E" );
  cursorxy( 2, 4 );
  printf( "  SS    N  N  N AAAAAA K K    EEEE" );
  cursorxy( 2, 5 );
  printf( "   SS   N   N N A    A K  K   E" );
  cursorxy( 2, 6 );
  printf( "     SS N    NN A    A K   K  E" );
  cursorxy( 2, 7 );
  printf( "SS   SS N     N A    A K    K EEEEEE" );
  cursorxy( 2, 8 );
  printf( " SSSSS " );
  cursorxy( 8, 12 );
  printf( "BY: MICHAEL PELLEGRINO" );
  cursorxy( 14, 14 );
  printf( "MARCH 2023" );
  cursorxy( 2, 18 );
  printf( "UP: I   DOWN: K   LEFT: U   RIGHT: O" );
  cursorxy( 8, 20 );
  printf( "PRESS ANY KEY TO START" );
  screen(1);

  // vv PAUSE
  poke( 0x00C6, 0 );
  jsr( 0xFFE4 );
  uint pausev = getchar();
  while( pausev == 0 )
    {
      pausev = getchar();
    }
  // ^^ PAUSE

  // vv shortcls
  lda( 0x93 );
  jsr( 0xFFD2 );

  // ^^ shortcls
  return;
}

uint playAgain()
{

  // clear a portion of the gameboard
  for( i = 9; i < 15; inc( i ) )
    {
      cursorxy( 4, i );
      printf( "                               " );
    }
  
  cursorxy( 14, 10 );
  printf( "GAME OVER!!" );
  longdelay();
  cursorxy( 12, 12 );
  printf( "PRESS Q TO QUIT" );
  cursorxy( 6, 13 );
  printf( "ANY OTHER KEY TO PLAY AGAIN" );
  clearkb();

  i = getchar();
  while( i == 0 )
    {
      i = getchar();
    }
  if( i == 81 )
    {
      i = 0;
    }
  else
    {
      i = 1;
    }
  return i;
}

void longdelay()
{
  for( j = 0x0000; j < 0xF904; j = j + 1 )
    {
      nop();
    }
  clearkb();
  return;
}

void setcolours()
{
  for( j = 0xD800; j < 0xD850; j = j + 1 )
    {
      poke( j, 1 );
    }
  for( j = 0xD850; j < 0xDBE8; j = j + 1 )
    {
      i = rnd(1);
      i = i & 0x0F;
      if( i == 0x06 )
	{
	  i = 1;
	}
      poke( j, i );
    }
  return;
}

void clearkb()
{
  poke( 198, 0 );
  jsr( 65508 );
  return;
}