1. use rops into a single pixel for more efficient work in melting?
2. turn off clipping for all rops to run faster?  (perhaps use a big canvas
   under the window, so all blasts, etc. will fit in the canvas even
   if not in the window).
4. Originally the idea was for this to be a networked game, with
   one person shooting missiles and the other blasting them down. Do this.
7. warp all popups to fit on screen.
8. make the different kinds of blast be pretty in color.
11. have little launching sites that open up.
12. have the save file save more things, like the city icon used.
16. Have an ifdef to eliminate pies.
17. Have a .sdirc, which points to a save_game file.
18. Mirv at other times than the top of the city window.
22. fix scores.