void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  pinMode(4, INPUT_PULLUP);
  pinMode(2, OUTPUT);
}
  

void loop() {
  if (digitalRead(4) == LOW) {
    digitalWrite(2, !digitalRead(2));
  delay(200);
  }
  
}