#include <FastLED.h>
#include "FastLED_additions.h"

#define LED_PIN     3
#define NUM_LEDS    17
#define LED_TYPE    WS2812
#define COLOR_ORDER GRB
CRGB leds[NUM_LEDS];

// how many LEDs in each ring
const uint8_t led_count[] = { 12, 6, 1};

CRGBPalette16 currentPalette = RainbowHalfStripeColors_p;

void setup() {
  FastLED.addLeds<LED_TYPE, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS);
}


void loop() {
  static uint16_t startIndex = 0, phase = 0;
  startIndex -= 1; /* rotation speed */
  phase += 1; /* swirl speed */

  CRGB *led = leds;
  for (uint8_t ring = 0; ring < 3 ; ring++) {
    uint16_t ringIndex = startIndex + sin16(phase + ring * 100);
    uint8_t count = led_count[ring];
    for (uint8_t i = 0; i < count ; i++) {
      uint16_t hue = ringIndex + i * 65535 / count;
      *led++ = ColorFromPaletteExtended(currentPalette, hue, 255, LINEARBLEND);
    }
  }
  FastLED.show();
}