// Blink onboard LED every 1 second
void setup() {
  pinMode(LED_BUILTIN, OUTPUT); // Set onboard LED pin as output
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH); // Turn LED ON
  delay(1000);                     // Wait for 1 second
  digitalWrite(LED_BUILTIN, LOW);  // Turn LED OFF
  delay(1000);                     // Wait for 1 second
}