def METHOD_NAME(self, event):
    if not self._button:
        return
    w, h = self.size
    x, y = event.pos
    sx = 2 * x / float(w) - 1.0
    sy = - (2 * y / float(h) - 1.0)
    if self._button == 1:
        self.target['position'][:] = sx, sy, 0
    elif self._button == 2:
        self.predator['position'][:] = sx, sy, 0