1. Various arcane values are tuned for pleasing affect.  For instance,
   blast size and number of increments (in circles.c), and delay between
   blast updates (in blast.c) are tuned for reasonable affect without taking
   too much cpu time. The melting procedure, the size of blasts, the size of
   cites, and the above-ground distance (BURST_DISTANCE) also all cooperate to
   create aesthetically pleasing city blowups (if there can be such a thing).

   Everything will WORK just fine without arcane tuning, it will just
   not look as good.

2. I have not bothered to find out much about the proper way to draw
   vectors, and thus the missile traces are really a kludge, and sometimes
   they miss the top or bottom of the screen.  But not often enough to
   fix, and perhaps its a feature--ICBM's from unusual directions.

3. Compiling with the DEBUG switch on does extra checking for consistency
   of the data structures, but this noticably affects performance.

4. I used a tab setting of four, not eight, when creating this code.