#include <FastLED.h>

#define NUM_LEDS 64
#define SPEED 20

CRGB leds[NUM_LEDS];

void setup() {
  FastLED.addLeds<WS2812B, 3, GRB>(leds, NUM_LEDS);
}

void loop() {
  // Sometimes you're just playing around and amazed by the results. Try this combination:
  leds[beatsin16((millis() / 1000) % 15 + 11, 0, NUM_LEDS - 1)] = CHSV(0, 255, 255);
  leds[beatsin16((millis() / 1000) % 30 + 5, 0, NUM_LEDS - 1)] = CHSV(160, 255, 255);

  // A variant that may work better on shorter strips:
  // leds[beatsin16(12, 0, NUM_LEDS - 1)] = CHSV(0, 255, 255);
  // leds[beatsin16(14, 0, NUM_LEDS - 1)] = CHSV(160, 255, 255);
  FastLED.show();
}