pong.c

#define PADDLEHEIGHT 5
#define BALLSIZE 3

short *PA = 0x8000;
short *PB = 0x8001;
short *DDRA = 0x8002;
short *DDRB = 0x8003;

short pbbuff;
short paddle;
short ballx;
short bally;
short dx;
short dy;
short score;
short i;
short j;
short k;
short buff[128][64];

void senddisp() {
	*PB = pbbuff & 0xFE;
	*PB = pbbuff | 0xFF;
}

void cls() {
	for (i = 0; i < 128; ++i) {
		for (j = 0; j < 64; ++j) {
			buff[i][j] = 0;
		}
	}
}

void writedisp() {
	short bytebuff;
	for (k = 0; k < 8; ++k) {
		bytebuff = 0;
		bytebuff |= buff[j][i*8 + k] << k;
	}
	*PA = bytebuff;
	senddisp();
}
			

void animate() {
	cls();
	
	//write the paddle to the buff
	for (i = 0; i < PADDLEHEIGHT; ++i)
		buff[0][paddle + i] = 1;
	
	//write the ball to the buff
	for (i = 0; i < BALLSIZE; ++i)
		for (j = 0; j < BALLSIZE; ++j)
			buff[ballx+i][bally+j] = 1;
	
	//write the score to the buff
	for (i = 0; i < score; ++i)
		buff[127-score/64][63-score%64] = 1;
	
	//write from the buff to the display
	for (i = 0; i < 8; ++i) {
		pbbuff = 0x47;
		*PA = 0xB8 | i;
		senddisp();
		*PA = 0x40;
		senddisp();
		pbbuff = 0x43;
		for (j = 0; j < 64; ++j) {
			writedisp();
		}
		pbbuff = 0x45;
		for (j = 64; j < 128; ++j) {
			writedisp();
		}
	}
}


void reset() {
	bally = paddle = 32;
	ballx = 64;
	dy = dx = 1;
	score = 0;
}

void step() {
	
	//check for x collision
	if (bally <= 0) 
		dy = 1;
	else if (bally + BALLSIZE - 1 >= 63)
		dy = -1;
	
	//check for y collision
	if (ballx < 0) {
		reset();
		return;
	} else if (ballx + BALLSIZE - 1 >= 127)
		ballx = -1;
	else if ((ballx == 1) && (bally >= paddle - BALLSIZE + 1) && (bally <= paddle + PADDLEHEIGHT - 1)) {
		dx = 1;
		++score;
	}
	
	//move the paddles
	if ((*PB & 0x30) == 0x10)
		paddle = (--paddle < 0 ? 0 : paddle);
	else if ((*PB & 0x30) == 0x30)
		paddle = (++paddle + PADDLEHEIGHT > 64 ? 64 - PADDLEHEIGHT : paddle);
	
	//animate the stuff
	bally += dy;
	ballx += dx;
	animate();
}

void delay() {
	for (i = 0; i < 0xFF; ++i)
		for (j = 0; j < 0xFF; ++j)
			for (k = 0; k < 0xFF; ++k)
				;
}

void main() {
	*DDRA = 0xFF;
	*DDRB = 0xCF;
	pbbuff = 0x47;
	*PA = 0x3F;
	senddisp();
	*PA = 0xC0;
	senddisp();
	reset();
	loop:
	step();
	delay();
	goto loop;
}