#include <FastLED.h>
#define LED_TYPE WS2812B  // type of RGB LED's
#define COLOR_ORDER GRB  // sequence of color
#define NUM_LEDS  300  // # of LED's
#define LED_PIN 2  // data pin on Arduino
#define BRIGHTNESS 200 // brightness range [0-255]

CRGB leds[NUM_LEDS];  // array for RGB control

void setup()
{
  FastLED.setMaxRefreshRate(0);
  FastLED.addLeds<LED_TYPE, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS);  // initializing definitions
  FastLED.setBrightness(BRIGHTNESS); // intializing brightness
}

void loop()
{
  CRGB TurnOnColor = CRGB::Blue;  // setting desired color
  CRGB TurnOffColor = CRGB::Black; // turning off LED
  int i;  // intializing counter
  int StripLength = 60;  // Length of the chasing strip

  for (i = 0; i < StripLength; i++)
  {
    leds[i] = TurnOnColor;
    FastLED.show();
  }

  for (i = StripLength; i < NUM_LEDS; i++)
  {
    leds[i] = TurnOnColor;
    leds[i-StripLength] = TurnOffColor;
    FastLED.show();
  }
  for(i = NUM_LEDS-StripLength; i <NUM_LEDS; i++)
  {
    leds[i] = TurnOffColor;
    FastLED.show();
  }
}