// Define LED pins
const int redLED1 = 2;
const int redLED2 = 17;
const int blueLED1 = 4;
const int blueLED2 = 16;

void setup() {
  // Initialize all LED pins as OUTPUT
  pinMode(redLED1, OUTPUT);
  pinMode(redLED2, OUTPUT);
  pinMode(blueLED1, OUTPUT);
  pinMode(blueLED2, OUTPUT);
}

void loop() {
  // --- Step 1: Red LEDs blink together ---
  digitalWrite(redLED1, HIGH);
  digitalWrite(redLED2, HIGH);
  delay(1000);
  digitalWrite(redLED1, LOW);
  digitalWrite(redLED2, LOW);
  delay(1000);

  // --- Step 2: Blue LEDs blink together ---
  digitalWrite(blueLED1, HIGH);
  digitalWrite(blueLED2, HIGH);
  delay(1000);
  digitalWrite(blueLED1, LOW);
  digitalWrite(blueLED2, LOW);
  delay(1000);

  // --- Step 3: One red + one blue together (pair 1) ---
  digitalWrite(redLED1, HIGH);
  digitalWrite(blueLED1, HIGH);
  delay(1000);
  digitalWrite(redLED1, LOW);
  digitalWrite(blueLED1, LOW);
  delay(1000);

  // --- Step 4: One red + one blue together (pair 2) ---
  digitalWrite(redLED2, HIGH);
  digitalWrite(blueLED2, HIGH);
  delay(1000);
  digitalWrite(redLED2, LOW);
  digitalWrite(blueLED2, LOW);
  delay(1000);
}