#include <FastLED.h>
#define LED_PIN 6
#define NUM_LEDS 21

// SEGMENTS
// 0 - A
// 1 - B
// 2 - C
// 3 - D
// 4 - E
// 5 - F
// 6 - G
int SEGMENTS[7][3] = {{0,1,2},{3,4,5},{6,7,8},{9,10,11},{12,13,14},{15,16,17},{18,19,20}};
CRGB leds[NUM_LEDS];

void setup() {

  FastLED.addLeds<WS2812, LED_PIN, GRB>(leds, NUM_LEDS);
  
}

void loop() {
  set_segment(0, CRGB(255, 0, 0));
  FastLED.show();
}

void set_segment(int segment_id, CRGB data) {
  int segment_leds[3] = {};
  segment_leds = SEGMENTS[segment_id];
  for(int i = 0; i < 3; i++) {
    leds[segment_leds[i]] = data;
  }
}