//https://wokwi.com/projects/378530029840033793
#include <FastLED.h>
#define NUM_LEDS 128
#define DATA_PIN 15
CRGB leds[NUM_LEDS];
void setup() { 
Serial.begin(115200);

  FastLED.addLeds<WS2812, DATA_PIN, GRB>(leds, NUM_LEDS);  // GRB ordering is typical 
}
void loop() { 
  for(int i=0;i < (NUM_LEDS/2);i++) {
    if(i%2==0) {
      leds[i]    = CRGB::Red;
  //    leds[i]    = CRGB(255,0,0);                //  zkouška přímého zadání rgb - funguje
    //  leds[i]   += CRGB( -255, 0, 0);        // minus takto ne 
      leds[i]   -= CRGB( 255, 0, 0);           //  změna barvy ulozeneho pixelu 
      leds[i]   += CRGB( 0, 0, 128);           //  změna barvy ulozeneho pixelu 
      leds[NUM_LEDS-1-i] = CRGB::Orange;
    } else {
      leds[i]    = CRGB::Lime;
      leds[NUM_LEDS -1 -i] = CRGB::Green;
    }
//Serial.println("A >>>");
//Serial.println(millis());
    FastLED.show();
//Serial.println(millis());
    delay(50);   // pro 64 i 128 LED to trvá cca 2 millis
  }
  for(int i=(NUM_LEDS/2)-1;i>=0;i--) {
    if(i%2==0) {
      leds[i]    = CRGB::Blue;
      leds[NUM_LEDS-1-i] = CRGB::White;
    } else {
      leds[i]    = CRGB::Yellow;
      leds[NUM_LEDS-1-i] = CRGB::Black;
    }
//Serial.println("B >>>");
//Serial.println(millis());
    FastLED.show();
//Serial.println(millis());
    delay(50);
  }
}