const int buttonPin = 26;
const int ledPins[] = {18, 5, 17, 16, 4};
const int numLEDs = 5;
bool ledsOn = false;

void setup() {
  Serial.begin(115200);
  for (int i = 0; i < numLEDs; i++) {
    pinMode(ledPins[i], OUTPUT);
    digitalWrite(ledPins[i], LOW);
  }
  pinMode(buttonPin, INPUT_PULLUP);
}

void loop() {
  if (digitalRead(buttonPin) == LOW) {
    ledsOn = !ledsOn;
    delay(200);
  }

  if (ledsOn) {
    for (int i = 0; i < numLEDs / 2; i++) {
      digitalWrite(ledPins[numLEDs / 2 - 1 - i], HIGH); 
      digitalWrite(ledPins[numLEDs / 2 + i], HIGH);      
      delay(2000);
      digitalWrite(ledPins[numLEDs / 2 - 1 - i], LOW);
      digitalWrite(ledPins[numLEDs / 2 + i], LOW);
    }
  }
}