N.BODY Control Keys

  Key        Action
======= ========================
  -->   Double the time step
  <--   Halve the time step
   I    Thrust selected body up
   M    Thrust selected body down
   J    Thrust selected body left
   K    Thrust selected body right
   O    Display relative to selected body
   Z    Clear display
   X    Zoom in 50%
   C    Zoom out 50%
<digit> Select body <digit>
        ("0"=center of mass)


   N.BODY variables
================================
C(i)  Color of body i
M(i)  Mass of body i
X(i)  X position of body i
Y(i)  Y position of body i
VX(i) X velocity of body i
VY(i) Y velocity of body i