A slightly modified main.c

main.c

#define F_CPU 1000000  // CPU frequency for proper time calculation in delay function
 
#include <avr/io.h>
#include <util/delay.h>
 
int main(void)
{
    DDRD |= (1 << PD6);  // make PD6 an output
 
    for(;;)
    {
        PORTD |= (1 << PD6);  // turn on PD6
        _delay_ms(500);  // delay for 500 ms
        PORTD |= (0 << PD6);  // turn off PD6
        _delay_ms(1000);  // delay for 1 s
    }
 
    return 0;  // the program executed successfully
}