Add switch to activate function

Hi, I'm 65 years old and I'm DIY. I am very impressed with programming but unfortunately I can't do it.

I would like to add to this program a function that will enable the effect once after giving 3.3V on the D4 input. I want to insert a button there.

Of course, I mean enabling CylonBounce

Thanks in advance. Greetings from Chechnya

#include "FastLED.h"
#define NUM_LEDS 60
CRGB leds[NUM_LEDS];
#define PIN 6

void setup()
{
  FastLED.addLeds<WS2811, PIN, GRB>(leds, NUM_LEDS).setCorrection( TypicalLEDStrip );
}

void loop() {
  CylonBounce(0xff, 0, 0, 4, 10, 50);
}

void CylonBounce(byte red, byte green, byte blue, int EyeSize, int SpeedDelay, int ReturnDelay){

  for(int i = 0; i < NUM_LEDS-EyeSize-2; i++) {
    setAll(0,0,0);
    setPixel(i, red/10, green/10, blue/10);
    for(int j = 1; j <= EyeSize; j++) {
      setPixel(i+j, red, green, blue);
    }
    setPixel(i+EyeSize+1, red/10, green/10, blue/10);
    showStrip();
    delay(SpeedDelay);
  }

  delay(ReturnDelay);

  for(int i = NUM_LEDS-EyeSize-2; i > 0; i--) {
    setAll(0,0,0);
    setPixel(i, red/10, green/10, blue/10);
    for(int j = 1; j <= EyeSize; j++) {
      setPixel(i+j, red, green, blue);
    }
    setPixel(i+EyeSize+1, red/10, green/10, blue/10);
    showStrip();
    delay(SpeedDelay);
  }
 
  delay(ReturnDelay);
}

void showStrip() {
 #ifdef ADAFRUIT_NEOPIXEL_H
   // NeoPixel
   strip.show();
 #endif
 #ifndef ADAFRUIT_NEOPIXEL_H
   // FastLED
   FastLED.show();
 #endif
}

void setPixel(int Pixel, byte red, byte green, byte blue) {
 #ifdef ADAFRUIT_NEOPIXEL_H
   // NeoPixel
   strip.setPixelColor(Pixel, strip.Color(red, green, blue));
 #endif
 #ifndef ADAFRUIT_NEOPIXEL_H
   // FastLED
   leds[Pixel].r = red;
   leds[Pixel].g = green;
   leds[Pixel].b = blue;
 #endif
}

void setAll(byte red, byte green, byte blue) {
  for(int i = 0; i < NUM_LEDS; i++ ) {
    setPixel(i, red, green, blue);
  }
  showStrip();
}

a common approach to reading a button is to configure the input with a pullup resistor

pinMode (ButPin, INPUT_PULLUP);

and with a momentary switch between the input pin and ground, check for a change in state and that the input pin state is LOW.

than condition can toggle a flag used to conditionally invoke other code in loop()