Envision a computer simulator for driving a car.  The simulator
provides various road conditions such as "regular", gravel, wet,
ice, etc.  The response to the car's controls, steering, braking,
etc., varies with the road conditions.  Use a State pattern to react
to the driver's use of the car controls.

For the purpose of this exercise, design a small GUI with four
buttons (labeled left, accel, right and brake), a choice of
conditions (labeled regular, gravel, wet and ice), and a feedback
textfield showing the effect (in an arbitrary scale) of pressing a
button in a given road condition as follows:

               Regular   Gravel    Wet     Ice
       accel      9        7        9       3
        left      5        3        4       1
       right      5        3        4       1
       brake      8        6        7       2

Hint: Obviously, one does not need to use the State pattern to
manage such a trivial state.  Pretend that the behavior of the car
in various conditions is determinted by the simulator using
complicated independent algorithms that are better encapsulated in
various states.

This exercise also shows:
  -  the MVC pattern
  -  a non-trivial layout
  -  inner anonymous classes
  -  a subtle point on scoping (see comments in Controller.java)