docs: def make_vel(self):
          "Make a set of velocities to be randomly chosen for emitted particles"
          self.vel = random.normal(self.vel_mu, self.vel_sigma, 16)
          # Make sure nothing's slower than 1/8 pixel / step
          for i, vel in enumerate(self.vel):
              if abs(vel) < 0.125 / self._size:
                  if vel < 0:
                      self.vel[i] = -0.125 / self._size
                  else:
                      self.vel[i] = 0.125 / self._size