explorer: The Expanding Civilization Simulation

The expanding civilization simulation (explorer.cpp, see Appendix B) used the same shell developed for milky. Modifications (such as double buffering) had to be made to allow for animation. Then, the various expansion models (see move1...move4, Appendix B) were introduced. Finally, a counter was added to compare the various models.

Figure 3: The black area has been taken over by an explorer civilization.