// Define the pins for the PIR sensor and LEDs
const int PIR_PIN = 2;
const int LED_1_PIN = 3;
const int LED_2_PIN = 4;
const int LED_3_PIN = 5;

// Define the LED sequence pattern
const int LED_SEQUENCE[] = {LED_1_PIN, LED_2_PIN, LED_3_PIN, LED_2_PIN, LED_1_PIN};
const int LED_SEQUENCE_LENGTH = sizeof(LED_SEQUENCE) / sizeof(LED_SEQUENCE[0]);

// Define the variable to store the current LED index
int currentLedIndex = 0;

void setup() {
  // Initialize the PIR sensor and LEDs
  pinMode(PIR_PIN, INPUT);
  pinMode(LED_1_PIN, OUTPUT);
  pinMode(LED_2_PIN, OUTPUT);
  pinMode(LED_3_PIN, OUTPUT);
}

void loop() {
  // Check if the PIR sensor is detecting something
  if (digitalRead(PIR_PIN) == HIGH) {
    // Turn on the current LED in the sequence
    digitalWrite(LED_SEQUENCE[currentLedIndex], HIGH);

    // Delay for a short time
    delay(2000);

    // Turn off the current LED in the sequence
    digitalWrite(LED_SEQUENCE[currentLedIndex], LOW);

    // Increment the LED index
    currentLedIndex = (currentLedIndex + 1) % LED_SEQUENCE_LENGTH;

    // If the LED index has reached the end of the sequence, reset it to 0
    if (currentLedIndex == 0) {
      delay(1000); // Wait for 1 second before resetting the sequence
    }
  } else {
    // Reset the LED sequence
    currentLedIndex = 0;
    digitalWrite(LED_1_PIN, LOW);
    digitalWrite(LED_2_PIN, LOW);
    digitalWrite(LED_3_PIN, LOW);
  }

  // Wait for a short time before checking the PIR sensor again
  delay(850);
}