---

//
int velocity = 0;

void setup()
{
  pinMode(2, INPUT);
  pinMode(4, INPUT);
  pinMode(11, OUTPUT);
}

void loop() {
if ( digitalRead(2) == HIGH ) {
  if ( velocity < 256 ) {
		analogWrite(11, velocity);
 		velocity = velocity + 1;
  }
}
else if ( digitalRead(4) == HIGH ) {
  if ( velocity > -1 ) {
	 	analogWrite(11, velocity);
		velocity = velocity - 1;
   }
}
delay(10);
}