Cylon_Simple.pde

#define cycleTime 150

void setup() {
  for(int i = 2; i < 13; i++)
    pinMode(i, OUTPUT);
}

void usePin(int pin) {
  for(int i = 2; i < 13; i++)
    digitalWrite(i, LOW);
  digitalWrite(pin, HIGH);
}

int p = 0;
int direction = 1;

void loop() {
  if(p >= 11) direction = -1;
  if(p <= 2)  direction = 1;

  usePin(p);

  p += direction;
  delay(cycleTime);
}