#define  LED_PIN1 5   // GPIO5
#define  LED_PIN2 18  // GPIO18
#define  LED_PIN3 19  // GPIO19
#define  LED_PIN4 21  // GPIO21

void setup() {
  pinMode(LED_PIN1, OUTPUT);
  pinMode(LED_PIN2, OUTPUT);
  pinMode(LED_PIN3, OUTPUT);
  pinMode(LED_PIN4, OUTPUT);
}

void loop() {  
  
  for (int i = 0; i < 10; i++) {  // Repeat the sequence 10 times

 // Turn on LEDs in sequence with a 100 ms delay
    digitalWrite(LED_PIN1, HIGH); // Turn the LED on
    delay(100); // Wait for 100 milliseconds
    digitalWrite(LED_PIN1, LOW); // Turn the LED off
    delay(100); // Wait for 100 milliseconds

    digitalWrite(LED_PIN2, HIGH); // Turn the LED on
    delay(100); // Wait for 100 milliseconds
    digitalWrite(LED_PIN2, LOW); // Turn the LED off
    delay(100); // Wait for 100 milliseconds

    digitalWrite(LED_PIN3, HIGH); // Turn the LED on
    delay(100); // Wait for 100 milliseconds
    digitalWrite(LED_PIN3, LOW); // Turn the LED off
    delay(100); // Wait for 100 milliseconds

    digitalWrite(LED_PIN4, HIGH); // Turn the LED on
    delay(100); // Wait for 100 milliseconds
    digitalWrite(LED_PIN4, LOW); // Turn the LED off
    delay(100); // Wait for 100 milliseconds
  }

  while (true) { // Stop further execution

  }
}