void setup() {
  pinMode(2, OUTPUT);
  pinMode(3, INPUT_PULLUP);
  pinMode(A0, INPUT);

}
int mode;
void loop() {
  int level = analogRead(A0);
  
  if (!digitalRead(3)) {
    mode++;
    if (mode > 3) {
      mode = 0;
    }
  }
  if (mode == 0) {
    if (analogRead(A0) < 500) {
      digitalWrite(2, HIGH);
    }
    else {
      digitalWrite(2, LOW);
    }
  }
  else if (mode == 1) {
    digitalWrite(2, HIGH);
  }
  else if (mode == 2) {
    digitalWrite(2, LOW);
  }
  else if (mode == 3) {
    digitalWrite(2, HIGH);
    delay(200);
    digitalWrite(2, HIGH);
    delay(200);
  }

    
    

}