#include <FastLED.h>
#define LED_PIN     7
#define NUM_LEDS    4
CRGB leds[NUM_LEDS];

int fadeAmount = 55;
int brightness = 0;

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

void loop() {

  brightness = brightness + fadeAmount;
  // reverse the direction of the fading at the ends of the fade: 
  if(brightness == 0 || brightness == 255)
  {
    fadeAmount = -fadeAmount ; 
  }
    
  for(int i=0;i<1;i++){
    leds[i] = CRGB::Black;
    leds[i].fadeLightBy(brightness);
    FastLED.show();
    delay(100);
  }
  
  for(int i=1;i<2;i++){
    leds[i] = CRGB::DarkOrange;
    leds[i].fadeLightBy(brightness);
    FastLED.show();
    delay(100);
  }

  for(int i=2;i<3;i++){
    leds[i] = CRGB::DarkOrange;
    leds[i].fadeLightBy(brightness);
    FastLED.show();
    delay(100);
  }

for(int i=3;i<4;i++){
    leds[i] = CRGB::Black;
    leds[i].fadeLightBy(brightness);
    FastLED.show();
    delay(100);
  }
}