int trigger = 4;
int echo = 5;

void setup() {
  pinMode(trigger, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(25, OUTPUT); // Green LED
  pinMode(26, OUTPUT); // Yellow LED
  pinMode(14, OUTPUT); // Red LED
  pinMode(21, OUTPUT); // Buzzer
  Serial.begin(9600); 
}

int finding_distance() {
  digitalWrite(trigger, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigger, LOW);
  float duration = pulseIn(echo, HIGH);
  return (duration * 0.034 / 2); 
}

void loop() {
  int distance = finding_distance();
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  if (distance >= 300) { 
    digitalWrite(25, HIGH);  // Green LED on
    digitalWrite(26, LOW);   // Yellow LED off
    digitalWrite(14, LOW);   // Red LED off
    noTone(21);              // Buzzer off
    Serial.println("You are safe");
  } else if (distance < 300 && distance >= 200) { 
    digitalWrite(25, LOW);   // Green LED off
    digitalWrite(26, HIGH);  // Yellow LED on
    digitalWrite(14, LOW);   // Red LED off
    tone(21, 500);           // Buzzer at very low frequency
    Serial.println("A ship is nearby");
  } else if (distance < 200 && distance >= 100) { 
    digitalWrite(25, LOW);   // Green LED off
    digitalWrite(26, LOW);   // Yellow LED off
    digitalWrite(14, HIGH);  // Red LED on
    tone(21, 3000);          // Buzzer at high frequency
    Serial.println("Danger ahead, buzzer on");
  } else {
    digitalWrite(25, LOW);   // Green LED off
    digitalWrite(26, LOW);   // Yellow LED off
    digitalWrite(14, LOW);   // Red LED off
    tone(21, 3000);          // Buzzer at high frequency
    Serial.println("Immediate danger, buzzer on");
  }
}