void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  pinMode(18, OUTPUT);
  pinMode(21, OUTPUT);
  pinMode(19, OUTPUT);
}

void loop() {
digitalWrite(18,1);
digitalWrite(21,0);
digitalWrite(19,0);
delay(500);
digitalWrite(18, 0);
digitalWrite(21,1);
digitalWrite(19,0);
delay(500);
digitalWrite(18,0);
digitalWrite(21,0);
digitalWrite(19,1);
delay(500);
Serial.println("looping");
}