public interface IPuzzle {

    public void resetPuzzle();          // restore puzzle to sorted state
    public boolean isSolved();          // return true is puzzle is in sorted state
    public boolean move(char dir);      // move a tile into the blank position
    public void scramble();             // scramble puzzle based on difficulty level
    public void display();              // print out current puzzle
    public void autoSolve();		// solve the puzzle automatically
}