#include "mbed.h"

DigitalOut leds[] = {(LED1), (LED2), (LED3), (LED4)};

int main()
{
    while(1)
    {
        int i;
        for(i=0;i<4;i++)
        {
            leds[0] = 0;
            leds[1] = 0;
            leds[2] = 0;
            leds[3] = 0;

            if(i==0 || i==3)
            {
                leds[i] = 1;
            }
            else
            {
                leds[i] = 1;
                leds[i+1] = 1;
            }
            wait(0.4);
        }
        for(i=3;i>=0;i--)
        {
            leds[0] = 0;
            leds[1] = 0;
            leds[2] = 0;
            leds[3] = 0;

            if(i==0 || i==3)
            {
                leds[i] = 1;
            }
            else
            {
                leds[i] = 1;
                leds[i-1] = 1;
            }

            wait(0.4);
        }
    }
}