#define Wireguide SENSOR_1
#define Left OUT_A
#define Right OUT_C
#define Threshold1 10
#define Threshold2 25
#define HysterVal 8

task main ()
{
  int Offset;
  int Hyster=0;
  int Diff;

  // The wire guidance sensor is used
  // the same way as a Light sensor
  SetSensor (Wireguide, SENSOR_LIGHT);

  // Reads the "no-signal" response. The sensor must
  // be centered on the wire, or generator be off
  Offset = Wireguide;
  Wait(200);

  // Starts driving

  OnFwd (Left+Right);
  while (true)
  {
    // Reads error signal
    Diff = Wireguide - Offset - Hyster;
    if (Diff >= -Threshold1 && Diff <= Threshold1)
    // We are centered - drive straight
    {
      OnFwd (Left+Right);
      Hyster = 0;
    }
    else
    {
      if (Diff > 0)
      {
        if(Diff > Threshold2)
        // Very off center: turn in place
        {
          OnRev (Left);
          OnFwd (Right);
        }
        else
        {
        // Slightly off center: shallow turn
          Off (Left);
          OnFwd (Right);
        }
        // sets hysteresis to avoid over-turning
        Hyster = HysterVal;
      }
      else
      {
        if(Diff < -Threshold2)
        {
          OnRev (Right);
          OnFwd (Left);
        }
        else
        {
          Off (Right);
          OnFwd (Left);
        }
        Hyster = -HysterVal;
      }
    }
  }
}