#define TRIG_PIN 9
#define ECHO_PIN 10
#define LED_PIN 6
#define BUZZER_PIN 7

void setup() {
  Serial.begin(9600);

    pinMode(TRIG_PIN, OUTPUT);
      pinMode(ECHO_PIN, INPUT);
        pinMode(LED_PIN, OUTPUT);
          pinMode(BUZZER_PIN, OUTPUT);
          }

          void loop() {
            digitalWrite(TRIG_PIN, LOW);
              delayMicroseconds(2);

                digitalWrite(TRIG_PIN, HIGH);
                  delayMicroseconds(10);

                    digitalWrite(TRIG_PIN, LOW);

                      long duration = pulseIn(ECHO_PIN, HIGH);

                        float distance = duration * 0.0343 / 2;

                          Serial.print("Distance: ");
                            Serial.print(distance);
                              Serial.println(" cm");

                                if (distance < 20) {
                                    digitalWrite(LED_PIN, HIGH);
                                        tone(BUZZER_PIN, 1500);
                                          }
                                            else if (distance < 50) {
                                                digitalWrite(LED_PIN, HIGH);
                                                    tone(BUZZER_PIN, 1000);
                                                        delay(150);
                                                            noTone(BUZZER_PIN);
                                                                digitalWrite(LED_PIN, LOW);
                                                                    delay(150);
                                                                      }
                                                                        else if (distance < 100) {
                                                                            digitalWrite(LED_PIN, HIGH);
                                                                                tone(BUZZER_PIN, 700);
                                                                                    delay(300);
                                                                                        noTone(BUZZER_PIN);
                                                                                            digitalWrite(LED_PIN, LOW);
                                                                                                delay(300);
                                                                                                  }
                                                                                                    else {
                                                                                                        digitalWrite(LED_PIN, LOW);
                                                                                                            noTone(BUZZER_PIN);
                                                                                                              }

                                                                                                                delay(100);
                                                                                                                }