Why all the balloons Converging at a single point

In this animation, balls fly out from one focus of the ellipse. Reflecting off the wall, they pass through the other focus—such is the geometric property of this curve.

The sum of the distances from one focus to any point on the ellipse and then to the second is always the same. Therefore, balls launched simultaneously at the same speed reach the meeting point together, even though they travel along different paths.