blink(1)

#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
#include <avr/power.h>
#endif
#define PIN            0
#define NUMPIXELS      21

Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

int delayval = 100;

void setup() {
  pixels.begin();
}

void loop() {

  // For a set of NeoPixels the first NeoPixel is 0, second is 1, all the way up to the count of pixels minus one.

  for(int i=-1;i<NUMPIXELS;){
if (i < NUMPIXELS-1){
      i++;
      pixels.setPixelColor(i, pixels.Color(0,255,0));

    pixels.show();
    delay(delayval);

}
else{
  for(i>=-1;i+1;){

     pixels.setPixelColor(i, pixels.Color(0,0,255));
    i--;
    pixels.show();
    delay(delayval);

  }
  }
  }
  }