const int ledPins[] = {10, 11, 12, 13}; 
const int numLeds = 4;                 
bool runBlinking = false;             

void setup() {
  Serial.begin(9600);  
  Serial.println("r - run s - stop ");                 
  for (int i = 0; i < numLeds; i++) {
    pinMode(ledPins[i], OUTPUT);       
  }
}

void loop() {
  if (Serial.available() > 0) {
    String command = Serial.readStringUntil('\n'); 
    command.trim();  
                                 
    if (command == "r") {
      runBlinking = true;   
    } else if (command == "s") {
      runBlinking = false;  
      turnOffLeds();        
    }
  }

  if (runBlinking) {
    blinkLeds();             
  }
}

void blinkLeds() {
  for (int i = 0; i < numLeds; i++) {
    digitalWrite(ledPins[i], HIGH);  // Turn the LED on
    delay(1000); 
    digitalWrite(ledPins[i], LOW);   // Turn the LED off
  }
  delay(500);                       // Wait for 500 milliseconds
}

void turnOffLeds() {
  for (int i = 0; i < numLeds; i++) {
    digitalWrite(ledPins[i], LOW);   // Turn off all LEDs
  }
}