#define BIT0 (1 << 0)
#define BIT1 (1 << 1)
#define BIT2 (1 << 2)
#define BIT3 (1 << 3)
#define BIT4 (1 << 4)
#define BIT5 (1 << 5)
#define BIT6 (1 << 6)
#define BIT7 (1 << 7)

static unsigned char i; // Main clock
static signed int x0, x1, x2;
static signed int y0, y1, y2;

void main(void) {
	// Calibrate internal oscillator
	asm {
	    bsf STATUS, RP0
	    call $3FF
	    movwf OSCCAL
	    bcf STATUS, RP0
	}
	
	OPTION_REG.NOT_GPPU = 0; // Enable pull-ups on GPIOs
	OPTION_REG.T0CS = 0; // Clock from Fosc/4
	OPTION_REG.PSA = 1; // Prescaler to WDT (not TMR0)
	
	TRISIO = ~(BIT0 | BIT1 | BIT2); // GPIOs 0 and 1 as outputs
	WPU = (BIT0 | BIT1 | BIT2); // Enable pull-ups
	
	// Seed oscillators
	x0 = 0;
	x1 = 11;
	
	y0 = 177;
	y1 = 181;
	
	for (i = 0; ; i++) {
	    unsigned char val = 0;
	    
	    if (i == 0) {
	        val |= BIT0;
	        
	        x2 = (x1 << 1) - (x1 >> 7) - x0;
	        x0 = x1;
	        x1 = x2;

	        y2 = (y1 << 1) - (y1 >> 7) - y0;
	        y0 = y1;
	        y1 = y2;
		}
		
	    if (i < (x2 + 66)) {
        	val |= BIT1;
		}
		
		if (i < (y2 + 66)) {
		    val |= BIT2;
		}

		GPIO = val;
	}
}