#define SESITYVITY_DIFF 65
#define MOTOR_SPEED 3 //0 to 9

int lastlevel;           // To store the previous level

task send_signal()
{
  while(true)
    {SendMessage(0); Wait(10);}
}

task check_signal()
{
  while(true)
  {
    lastlevel = SENSOR_1;
    if(SENSOR_1 > lastlevel + SESITYVITY_DIFF)
    {
     //OnRev(OUT_C); Wait(85); OnFwd(OUT_A+OUT_C);
     Off(OUT_A+OUT_C);
     SetPower(OUT_A+OUT_C,9); //take turn with full power
     SetDirection(OUT_A+OUT_C,OUT_TOGGLE);
     PlaySound(1);PlaySound(1);
     On(OUT_A+OUT_C);
     turn_around(75);
     SetPower(OUT_A+OUT_C,MOTOR_SPEED);
     //Wait(500);
    }
  }
}
void turn_around(int turntime)
{
  Off(OUT_C);
  Wait(turntime);
  On(OUT_C);
  SetDirection(OUT_A+OUT_C,OUT_TOGGLE);
}

task main()
{
  SetPower(OUT_A+OUT_C,MOTOR_SPEED);
  SetSensorType(SENSOR_1, SENSOR_TYPE_LIGHT);
  SetSensorMode(SENSOR_1, SENSOR_MODE_RAW);
  OnRev(OUT_A+OUT_C);
  start send_signal;
  start check_signal;
}