#define LED_PIN_A4 A4  // Define the pin for the first LED
#define LED_PIN_A5 A5  // Define the pin for the second LED

int brightnessA4 = 0;  // Current brightness level for LED A4
int brightnessA5 = 255; // Current brightness level for LED A5 (starting from fully on)
int fadeAmount = 5;    // How much to change the brightness

void setup() {
  pinMode(LED_PIN_A4, OUTPUT);  // Set the A4 LED pin as an output
  pinMode(LED_PIN_A5, OUTPUT);  // Set the A5 LED pin as an output
}

void loop() {
  // Fade in for LED on A4 and fade out for LED on A5
  for (brightnessA4 = 0; brightnessA4 <= 255; brightnessA4 += fadeAmount) {
    analogWrite(LED_PIN_A4, brightnessA4);  // Set the brightness of the LED on A4
    analogWrite(LED_PIN_A5, brightnessA5);  // Set the brightness of the LED on A5
    brightnessA5 -= fadeAmount;              // Decrease brightness for A5
    delay(30);                               // Wait for 30 milliseconds
  }

  // Fade out for LED on A4 and fade in for LED on A5
  for (brightnessA4 = 255; brightnessA4 >= 0; brightnessA4 -= fadeAmount) {
    analogWrite(LED_PIN_A4, brightnessA4);  // Set the brightness of the LED on A4
    analogWrite(LED_PIN_A5, brightnessA5);  // Set the brightness of the LED on A5
    brightnessA5 += fadeAmount;              // Increase brightness for A5
    delay(30);                               // Wait for 30 milliseconds
  }
}