// https://www.reddit.com/r/FastLED/comments/1gqb494/advice_for_using_clusters_of_leds_as_pixels/

#include <FastLED.h>

#define NUM_LEDS (4 * 16)
CRGBArray<NUM_LEDS> leds;

CRGBSet const sets[] = {
  leds(0, 15),
  leds(16, 31),
  leds(32, 47),
  leds(48, 63),
};


void setup() {
  FastLED.addLeds<WS2812B, 2, GRB>(leds, NUM_LEDS);
}


void loop() {
  static uint8_t n = 0;
  sets[n].fill_solid(CRGB::White);
  n = (n + 1) % 4;
  FastLED.show();
  FastLED.clear();
  delay(250);
}