#include "FastLED.h"
#define NUM_LEDS 60
CRGB leds[NUM_LEDS];
#define PIN 6

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

void loop() 
{
  meteorRain(CRGB(0x00,0x00,0x00), CRGB(0xff,0xff,0xff),10 ,120 ,true, 40);
} 

void meteorRain(CRGB ColorBackground, CRGB ColorMeteor, byte meteorSize, byte meteorTrailDecay, boolean meteorRandomDecay, int SpeedDelay) 
{  
  // set background color
  fill_solid( leds, NUM_LEDS, ColorBackground );

  for(int i = 0; i < NUM_LEDS; i++) 
  {
    // fade color to background color for all LEDs
    for(int j=0; j < NUM_LEDS; j++) {
      if( (!meteorRandomDecay) || (random(10) > 5) ) {
        leds[j] = fadeTowardColor(leds[j], ColorBackground, meteorTrailDecay ); 
      }
    }

    // draw meteor
    for(int j = 0; j < meteorSize; j++) {
      if( ( i-j < NUM_LEDS) && (i-j >= 0) ) {
        leds[i-j]= ColorMeteor;
      }
    }
   
    FastLED.show();
    delay(SpeedDelay);
  }
}

// Functions from Kriegsman example
CRGB fadeTowardColor( CRGB& cur, const CRGB& target, uint8_t amount)
{
  nblendU8TowardU8( cur.red,   target.red,   amount);
  nblendU8TowardU8( cur.green, target.green, amount);
  nblendU8TowardU8( cur.blue,  target.blue,  amount);
  return cur;
}

// function used by "fadeTowardColor"
void nblendU8TowardU8( uint8_t& cur, const uint8_t target, uint8_t amount)
{
  if( cur == target) return;
  
  if( cur < target ) {
    uint8_t delta = target - cur;
    delta = scale8_video( delta, amount);
    cur += delta;
  } else {
    uint8_t delta = cur - target;
    delta = scale8_video( delta, amount);
    cur -= delta;
  }
}