//connect 8 leds to port L glow 0-3 leds one by one
#include <stdint.h>

#define DDRL  (*(volatile uint8_t*)0x10A)
#define PORTL (*(volatile uint8_t*)0x10B)

void delay1sec(void){
    TCNT1  = 0;
    TCCR1A = 0x00;
    TCCR1B = 0x05;          

    while (TCNT1 < 15625);

    TCCR1B = 0x00;          
}

void setup() {
    DDRL |= (1<<0) | (1<<1) | (1<<2) | (1<<3);   
}

void loop() {
    for (uint8_t i = 0; i < 4; i++) {
        PORTL = (1 << i);   
        delay1sec();
        PORTL = 0x00;       
        delay1sec();
    }
}