// Jeff Ritchie 2 15 2026 revision -traveling pulse
//  based on adafruit neopixel example sketch
#include <Adafruit_NeoPixel.h>//pulls the Neopixel library
#ifdef __AVR__ //if an AVR board, use the library below. RP2040 is not an AVR. 
  #include <avr/power.h>
#endif
#define PIN        D6 //RP2040 uses D6 rather than pin 6
#define NUMPIXELS 56 //

Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRBW + NEO_KHZ800); //creates an instance called pixels
//third parameters indicate color in green red blue white order and the signal frequency of 800khz
#define DELAYVAL 30 //sets delay variable that makes it easier to change. Originally 500ms

void setup() {
#if defined(__AVR_ATtiny85__) && (F_CPU == 16000000)
  clock_prescale_set(clock_div_1);
#endif

  pixels.begin();
}

void loop() {
  static int center = 0;
  for(int i=0; i<NUMPIXELS; i++) {
    int distance = abs(i - center);
    int brightness = max(0, 150 - distance * 25);
    pixels.setPixelColor(i, pixels.Color(brightness, 0, 0));
  }
  pixels.show();
  center++;
  if(center >= NUMPIXELS) center = 0;
  delay(DELAYVAL);
}