class Command {
public:
    virtual ~Command();

    virtual void Execute() = 0;
protected:
    Command();
};

// game programming patterns
class Command
{
public:
  virtual ~Command() {}
  virtual void execute() = 0;
};

class Command
{
public:
  virtual ~Command() {}
  virtual void execute(GameActor& actor) = 0;
};

class Command
{
public:
  virtual ~Command() {}
  virtual void execute() = 0;
  virtual void undo() = 0;
};