// Define states
enum TrafficLightState {
  RED,
  YELLOW,
  GREEN
};

// Initialize the current state
TrafficLightState currentState = RED;

// Define timing constants
const unsigned long redDuration = 2000;    // 2 seconds
const unsigned long yellowDuration = 1000; // 1 second
const unsigned long greenDuration = 2000;  // 2 seconds

unsigned long previousMillis = 0;

void setup() {
  pinMode(1, OUTPUT);  // Red LED on pin 1
  pinMode(2, OUTPUT);  // Yellow LED on pin 2
  pinMode(3, OUTPUT);  // Green LED on pin 3
}

void loop() {
  unsigned long currentMillis = millis();

  switch (currentState) {
    case RED:
      digitalWrite(1, HIGH);
      digitalWrite(2, LOW);
      digitalWrite(3, LOW);
      if (currentMillis - previousMillis >= redDuration) {
        currentState = YELLOW;
        previousMillis = currentMillis;
      }
      break;

    case YELLOW:
      digitalWrite(1, LOW);
      digitalWrite(2, HIGH);
      digitalWrite(3, LOW);
      if (currentMillis - previousMillis >= yellowDuration) {
        currentState = GREEN;
        previousMillis = currentMillis;
      }
      break;

    case GREEN:
      digitalWrite(1, LOW);
      digitalWrite(2, LOW);
      digitalWrite(3, HIGH);
      if (currentMillis - previousMillis >= greenDuration) {
        currentState = RED;
        previousMillis = currentMillis;
      }
      break;
  }
}