#include <Adafruit_NeoPixel.h>

/* Change LEDS to the number of your leds */
#define LEDS 43

#define PIN 3

#define RED 255
#define GREEN 64
#define BLUE 0

Adafruit_NeoPixel strip(LEDS, PIN);

float SPEED[LEDS];

float getIntensity(const unsigned int *id, const unsigned long *timestamp) {
  return 0.1 + (cos((float)*timestamp * 0.01 * SPEED[*id]) + 1.0) * 0.45;
}

void setup() {
  strip.begin();
  strip.show();

  for (int s = 0; s < LEDS; s++) {
    SPEED[s] = (float)random(100, 1000) / 1000.0;
  }
}

void loop() {
  unsigned long timestamp = millis();

  for (int led = 0; led < LEDS; led++) {
    float intensity = getIntensity(&led, &timestamp);

    strip.setPixelColor(
      led,
      (float)RED * intensity,
      (float)GREEN * intensity,
      (float)BLUE * intensity
    );
  }

  strip.show();

  delay(2);
}