// https://wokwi.com/projects/438176050010628097

# include <FastLED.h>

# define NUM_LEDS 299
# define COLOR_ORDER GRB

CRGB leds[NUM_LEDS];

# define PRESSED LOW
# define DATA_PIN 4
# define theButton 2

void setup() {

   Serial.begin(115200);
   Serial.println("\nThis is actually painful.\n");
   
   FastLED.addLeds<WS2811, DATA_PIN, GRB>(leds, NUM_LEDS);
   FastLED.setBrightness(255);  // 84 = dim
   
   pinMode(theButton, INPUT_PULLUP);

}

void loop() {
  if (digitalRead(theButton) == PRESSED) {
    Serial.print("cycle intitiated...");
    Serial.flush();
    runSAMD21();
    Serial.println("  ... and complete.");
  }
}   

void setLedColor(int colorStep)
{
  int r = colorStep; 
  int b = 255 - colorStep;
  int g = 0;

  for(int x = 0; x < NUM_LEDS; x++)
       leds[x] = CRGB(r, g, b);

   FastLED.show();
}

void runSAMD21() {
  for (int colorStep = 0; colorStep < 256; colorStep++)
    setLedColor (colorStep);

  for (int colorStep = 255; colorStep > -1; colorStep--)
    setLedColor (colorStep);
}