Like the original "Missile Command" and its clones, this game
places  you  in  control  of  Anti-ICBM weapons which you use to 
destroy  an  onslaught of missiles (and other nasties) which are 
dropping onto your nation.
   The game ends when your cities have all  been  destroyed. You 
only   gain   replacement   cities  by  acheiving  certain score
thresholds during each attack (level).
   The main difference between this game and  Missile Command is
that ICBM3D, as the name  suggests,  provides  a 3D perspective. 
You take advantage of X-Window's  3-button mouse to control your
firing  sight  ("cross-hair")  in  3-dimensions, and change your 
viewpoint.

WWW: http://www.sonic.net/~nbs/unix/x/icbm3d