Change Direction of Lights using C

I have a set of lights ws2812 tha are addressible using the FASTLED library on a Arduino writen in C .

The code below makes this animation:  ○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙○◙ --------->  on a LED strip

The lights are working great in its current direction. I need the lights to travel now in the opposite direction.  Thank you.

#include <FastLED.h>

// Define the array of leds
#define LED_DT 3
#define COLOR_ORDER GRB
#define LED_TYPE WS2812
#define NUM_LEDS 38
uint8_t max_bright = 255;
struct CRGB leds[NUM_LEDS];


void setLEDs (int K, int N) {
  FastLED.clear();
for (int i = 0; i < NUM_LEDS; i++) {
    //( int i = NUM_LEDS-1; i >=0; i–-)  //  tried this but it didnt work
    if (i % N == K) leds[i].setRGB (0, 0, 250); // set red LED
  }
  FastLED.show();
}

void setup() {
  delay (1000);
  LEDS.addLeds<LED_TYPE, LED_DT, COLOR_ORDER>(leds, NUM_LEDS);
  FastLED.setBrightness(max_bright);
}

void loop() {
  int N = 5;
  for  (int i = 0; i < N; i++) {
    setLEDs (i, N);
    delay (150);
  }
}

Select allOpen in new window