Twiddling bit with XOR operation

xor.c

// ------- Preamble ------- //
#include <avr/io.h>
#include <util/delay.h>                     /* Time delay function */

#define DELAYTIME	250                     /* milliseconds */
#define LED_PORT	PORTB
#define LED_DDR		DDRB

int main(void) {

	uint8_t i;
	uint8_t z;
	
	// ------- Inits ------- //
	LED_DDR = 0xff;							/* all LEDs are configured for output */
	
	// ------- Event loop ------- //
	while(1) {
		
		LED_PORT = 0;
		z = 0x00000000;
		_delay_ms(DELAYTIME);
		
		for (i=0; i<6; i++) {
			z |= _BV(i);					// z |= (1 << i);
			LED_PORT ^= z;
			_delay_ms(DELAYTIME);
		}
		//LED_PORT = 0;
		_delay_ms(DELAYTIME * 2);
		
	}
	
	return(0);								/* this line is never reached */
}