// Define LED pins
#define RED_LED 18       // Red LED connected to GPIO 18
#define YELLOW_LED 19    // Yellow LED connected to GPIO 19
#define GREEN_LED 21     // Green LED connected to GPIO 21

void setup() {
  // Set LED pins as output
  pinMode(RED_LED, OUTPUT);    // Configure RED_LED pin as output
  pinMode(YELLOW_LED, OUTPUT); // Configure YELLOW_LED pin as output
  pinMode(GREEN_LED, OUTPUT);  // Configure GREEN_LED pin as output
}

void loop() {
  // Red light on for 5 seconds (Stop signal)
  digitalWrite(RED_LED, HIGH);     // Turn on red LED
  digitalWrite(YELLOW_LED, LOW);   // Ensure yellow LED is off
  digitalWrite(GREEN_LED, LOW);    // Ensure green LED is off
  delay(5000);                     // Wait for 5 seconds

  // Yellow light on for 2 seconds (Warning signal)
  digitalWrite(RED_LED, LOW);      // Turn off red LED
  digitalWrite(YELLOW_LED, HIGH);  // Turn on yellow LED
  digitalWrite(GREEN_LED, LOW);    // Ensure green LED is off
  delay(2000);                     // Wait for 2 seconds

  // Green light on for 5 seconds (Go signal)
  digitalWrite(RED_LED, LOW);      // Ensure red LED is off
  digitalWrite(YELLOW_LED, LOW);   // Ensure yellow LED is off
  digitalWrite(GREEN_LED, HIGH);   // Turn on green LED
  delay(5000);                     // Wait for 5 seconds
}