int led = 4;
int button = 3;
int buttonState = 0;
int x = 0;

void setup() {
  pinMode(led, OUTPUT);
  pinMode(button, INPUT);
}

void loop() {
  buttonState = digitalRead(button);
  if (buttonState == LOW) {
    for (int times = 0; times < 20; times++) {
      for (int brightness = 0; brightness < 255; brightness++) {
        analogWrite(led, brightness);
        delay(20);
      }
      // fade the LED on Pin 4 from brightest to off:
      for (int brightness = 255; brightness >= 0; brightness--) {
        analogWrite(led, brightness);
        delay(20);
      }
    }
  }
  else {
    analogWrite(led, 0);
  }
}