void setup() {
 
pinMode(11, OUTPUT);
pinMode(10, OUTPUT);

}

void loop() {
  for (int x = 0; x < 256; x++)
  {
    analogWrite(11, x);
    delay(10);
  }
 for (int x = 256; x >= 0; x--)
 {
  analogWrite(10, x);
  delay(10);
 }
 
}