Orca

  Write a class called Orca that extends the Critter
   class.  The instances of the Orca class follow a pattern of moving forward
   four times, then turning around, then moving back four times and turning
   around again so that they return to their original position and direction.
   Each Orca is always either in moving-mode or in turning-mode.  They start
   out in moving-mode.  While in moving-mode, they try to hop forward if
   possible until they have hopped four times, at which point they switch into
   turning-mode.  If it is not possible to hop while in moving-mode, an Orca
   instead infects whatever is in front of it.  When in turning-mode, the Orca
   turns left twice and then switches back to moving-mode.  Don't worry about
   the fact that if the Orca encounters a wall while in moving-mode, it gets
   stuck trying to infect the wall indefinitely.  The Orca displays itself as
   "M" while in moving-mode and as "T" while in turning-mode.  Its color should
   be the default color for critters.