const int redPins[] = {2, 5, 8, 11};      // Red LEDs for each lane
const int amberPins[] = {3, 6, 9, 12};    // Amber LEDs
const int greenPins[] = {4, 7, 10, 13};   // Green LEDs

// Timing constants
const unsigned long greenDuration = 5000;   // Time each green stays on
const unsigned long amberDuration = 2000;   // Amber delay = 2 sec
const unsigned long redDelay = 5000;        // Red delay = 5 sec

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

  setInitialLights();
}

void loop() {
  for (int i = 0; i < 4; i++) {
    int next = (i + 1) % 4;

    // Step 1: Current (i) and Next (next) to Amber
    digitalWrite(greenPins[i], LOW);
    digitalWrite(amberPins[i], HIGH);
    digitalWrite(redPins[next], HIGH);  // Make sure next lane is Red
    delay(amberDuration);

    // Step 2: Current to Red, wait 5 sec, then Next to Green
    digitalWrite(amberPins[i], LOW);
    digitalWrite(redPins[i], HIGH);    // Current lane turns Red
    delay(redDelay);                   // Wait 5 sec

    digitalWrite(greenPins[next], HIGH); // Next lane Green
    digitalWrite(redPins[next], LOW);
    delay(greenDuration);
  }
}

// Set startup state: Lane 1 green, rest red
void setInitialLights() {
  for (int i = 0; i < 4; i++) {
    digitalWrite(redPins[i], HIGH);    // All Red by default
    digitalWrite(amberPins[i], LOW);
    digitalWrite(greenPins[i], LOW);
  }

  digitalWrite(redPins[0], LOW);       // Lane 1 = Green
  digitalWrite(greenPins[0], HIGH);
}