#define LED_BUILTIN 2  // Internal LED on ESP or Arduino Uno (Pin 13 on Uno)

void setup() {
    pinMode(LED_BUILTIN, OUTPUT);  // Set internal LED 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
}