#define PINA 8
#define PINB 9
#define PINC 10
#define PIND 11

int pins[] = {PINA, PINB, PINC, PIND};

void setup() {
  for (int i=0; i<4; i++) {
    pinMode(pins[i], OUTPUT);
  }
}

void step(int s) {
  if (s<0 || s>7) {
    for (int i=0; i<4; i++) {
      digitalWrite(pins[i], LOW);
    }
  } else {
    int on = LOW;
    for (int i=0; i<4; i++) {
      if (i==s/2 || i==(s/2+s%2)%4) {
        on = HIGH;
      } else {
        on = LOW;
      }
      digitalWrite(pins[i], on);
    }  
  }
}

int dly = 1;

void loop() {
  for (int i=0; i<512; i++) {
    step(i % 8);
    delay(dly);
  }
  step(-1);
  delay(200);
  for (int i=511; i>0; i--) {
    step(i % 8);
    delay(dly);
  }
  step(-1);
  delay(500);
}