Long_Frag routine explanation:
This routine is used to check whether an ememy can be hit with missile
splash damage, by firing a missile into a wall or mine next to it. The
diagram below shows how this is used:
Here, Torque (marked with green) fires a missile at the area of wall on
the right of the screen. The enemy cybug (blue) is close enough to the
impact area to receive some damage.
This routine is normally called directly after an exchange of missiles
between the two cybugs. When en enemy moves out of Torque's firing line,
he GPS-scans the square directly
behind the place where the enemy last was. The coordinates of this square
are stored in ~vx and ~vy when the long_frag routine is called.
