const int ledPin1 = 10;
const int ledPin2 = 11;
const int buttonPin = 2;

void setup() {
  pinMode(ledPin1, OUTPUT);
  pinMode(ledPin2, OUTPUT);
  pinMode(buttonPin, INPUT);
}

void loop() {
  int buttonState = digitalRead(buttonPin);

  if (buttonState == HIGH) {
    for (int i = 0; i <= 255; i += 5) {
      analogWrite(ledPin1, i);
      delay(50);
    }
    for (int i = 255; i >= 0; i -= 5) {
      analogWrite(ledPin1, i);
      delay(50);
    }
    for (int i = 0; i <= 255; i += 5) {
      analogWrite(ledPin2, i);
      delay(50);
    }
    for (int i = 255; i >= 0; i -= 5) {
      analogWrite(ledPin2, i);
      delay(50);
    }
  }
}