Test

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#include <Arduino.h>
#include <FastLED.h>

#define DATA_PIN 12
#define WIDTH 16
#define HEIGHT 16
#define NUM_LEDS WIDTH*HEIGHT

CRGB leds[NUM_LEDS];

int XY(int x, int y) {
  if (y%2 == 0)
    return y * WIDTH + x;
  else
    return (y + 1) * WIDTH - x - 1;
}

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

  for ( int y = 0; y < HEIGHT; y++ ) {
    for ( int x = 0; x < WIDTH; x++ ) {
      leds[XY(x,y)] = CRGB::Red;
      FastLED.show();
      delay(100);
    }
  }
  
}

void loop() {
}