int redPins[] = {1, 4, 7, 10};    // Red light pins
int yellowPins[] = {2, 5, 8, 11}; // Yellow light pins
int greenPins[] = {3, 6, 9, 12};  // Green light pins

void setup() {
  // Set all pins as OUTPUT
  for (int i = 0; i < 4; i++) {
    pinMode(redPins[i], OUTPUT);
    pinMode(yellowPins[i], OUTPUT);
    pinMode(greenPins[i], OUTPUT);
  }

  // Ensure all lights start as RED
  for (int i = 0; i < 4; i++) {
    digitalWrite(redPins[i], HIGH);   // All red ON
    digitalWrite(yellowPins[i], LOW); // All yellow OFF
    digitalWrite(greenPins[i], LOW);  // All green OFF
  }
}

void loop() {
  for (int i = 0; i < 4; i++) { // Loop through each traffic light
    // Ensure all lights remain RED except the active one
    for (int j = 0; j < 4; j++) {
      digitalWrite(redPins[j], HIGH);
      digitalWrite(yellowPins[j], LOW);
      digitalWrite(greenPins[j], LOW);
    }
 delay(1000);
    // Activate GREEN for the current traffic light
    digitalWrite(redPins[i], LOW);  // Turn off red
    digitalWrite(greenPins[i], HIGH); // Turn on green
    delay(1000); // Green for 1 second

    // Change to YELLOW
    digitalWrite(greenPins[i], LOW);
    digitalWrite(yellowPins[i], HIGH); // Turn on yellow
    delay(1000); // Yellow for 1 second

    // Change back to RED
    digitalWrite(yellowPins[i], LOW);
    digitalWrite(redPins[i], HIGH); // Turn on red
    delay(1000); // Red for 1 second
  }
}