#include <Arduino.h>

const int ledArray[16] = {13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 14, 15, 16, 17};
const int ledArrayLen = 16;

void setup() {
  // put your setup code here, to run once:
  for (int i = 0; i < ledArrayLen; i++) {
    pinMode(ledArray[i], OUTPUT);
    digitalWrite(ledArray[i], LOW);
  }
}

void loop() {
  // put your main code here, to run repeatedly:
  // blink all for 3 times
  for (int i = 0; i < 3; i++) {
    for (int j = 0; j < ledArrayLen; j++) 
      digitalWrite(ledArray[j], HIGH);
    delay(500);
    for (int j = 0; j < ledArrayLen; j++) 
      digitalWrite(ledArray[j], LOW);
    delay(500);
  }
  // led chasing twice, each lasted 16*0.025 secs
    for (int j = 0; j < ledArrayLen; j++) {
      digitalWrite(ledArray[j], HIGH);
      delay(25);
      digitalWrite(ledArray[j], LOW);
      delay(25);
    }
    for (int j = ledArrayLen-1; j > 0; j--) {
      digitalWrite(ledArray[j], HIGH);
      delay(25);
      digitalWrite(ledArray[j], LOW);
      delay(25);
    }
  // wait for 250 msecs
  delay(250);
}