#define LED0 PB0
#define LED1 PB1
#define LED2 PB3
#define LED3 PB4
#define LED4 PB5
#define LED5 PB6
#define LED6 PB7
#define LED7 PB8
int pos = 0;

void setup() {
pinMode(LED0, OUTPUT);
pinMode(LED1, OUTPUT);
pinMode(LED2, OUTPUT);
pinMode(LED3, OUTPUT);
pinMode(LED4, OUTPUT);
pinMode(LED5, OUTPUT);
pinMode(LED6, OUTPUT);
pinMode(LED7, OUTPUT);
}

void loop() {

  switch(pos){
    case 0:
      digitalWrite(LED0,HIGH);
        digitalWrite(LED1,LOW);
        digitalWrite(LED2,LOW);
        digitalWrite(LED3,LOW);
        digitalWrite(LED4,LOW);
        digitalWrite(LED5,LOW);
        digitalWrite(LED6,LOW);
        digitalWrite(LED7,LOW);
      break;
    case 1:
      digitalWrite(LED1,HIGH);
      break;
    case 2:
      digitalWrite(LED2,HIGH);
      break;
    case 3:
      digitalWrite(LED3,HIGH);
      break;
    case 4:
      digitalWrite(LED4,HIGH);
      break;
    case 5:

      digitalWrite(LED5,HIGH);
      break;
    case 6:
      digitalWrite(LED6,HIGH);
      break;
    case 7:
      digitalWrite(LED7,HIGH);
      pos = (pos*-1);
      break;
  }
  pos++;
  delay(100);
}