   Beginner question
  What is the easiest way to make a magic projectile have a "sine wave" sinusoidal trajectory? Details are appreciated.   
  Well I can't provide much detail, but you're going to want to look into splines/curves.  A google search might turn up some interesting stuff.   ;  Make the projectile follow the normal path of a projectile, i.e. the overall path of the projectile, but then displace this using a sine-wave.e.g.Vector position = calculatePositionOnPath(time) + calculateSineOffset(time);   