int pulseWidth=0;
int rise=5;
boolean forward=true;

void setup() {
  // put your setup code here, to run once:
  pinMode (10, OUTPUT);
  pinMode (12, OUTPUT);
  pinMode (11, OUTPUT);
  digitalWrite (12, HIGH);
  digitalWrite (11, LOW);

}

void loop() {
  // put your main code here, to run repeatedly:
  pulseWidth = pulseWidth + rise;
  analogWrite (10, pulseWidth);
 
  //here's where we'll reverse the motor direction if the speed is at 0.
  if (pulseWidth <=0) {
    forward = !forward;
    rise = -rise;
  }
  if (forward == true){
    digitalWrite (12, HIGH);
    digitalWrite (11, LOW);
  }
  else {
    digitalWrite (12, LOW);
    digitalWrite (11, HIGH);
  }
    
  if (pulseWidth >= 255){
    rise = -rise;
  }
  delay (50);
}