const int seatPin = D2;
const int beltPin = D3;
const int ignitionPin = D4;
const int speedPin = D5;

const int ledPin = D8;
const int buzzerPin = D9;

void setup() {

  pinMode(seatPin, INPUT_PULLUP);
  pinMode(beltPin, INPUT_PULLUP);
  pinMode(ignitionPin, INPUT_PULLUP);
  pinMode(speedPin, INPUT_PULLUP);

  pinMode(ledPin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);

  digitalWrite(ledPin, LOW);
  noTone(buzzerPin);
}

void loop() {

  bool seat = digitalRead(seatPin) == LOW;
  bool belt = digitalRead(beltPin) == LOW;
  bool ignition = digitalRead(ignitionPin) == LOW;
  bool speed = digitalRead(speedPin) == LOW;

  digitalWrite(ledPin, LOW);
  noTone(buzzerPin);

  if (seat && ignition) {

    if (!belt) {

      digitalWrite(ledPin, HIGH);

      if (speed) {
        tone(buzzerPin, 1000);
      }

    }

  }

  delay(20);
}