Basic implementation of the n-body problem.
- space bar -> start simulation
- a/q -> increase/decrease number of initial bodies
- z/s -> +10/-10 for the number of initial bodies
- e/d -> increase/decrease the magnitude of the gravity
- r/f -> increase/decrease the mass factor
- t/g -> increase/decrease the mass of the sun
- o/l -> increase/dicrease the initial density of the bodies