Fixed bug in pong demo where ball does not reset to center.

[grimatoma]

The initial position is set as the vector2 of Position but Position is a pointer so it updates meaning the initial position is the current position of the ball

[paulloz]

Vector2 is a struct, and as such is copied on assignment. So both of those lines will yield the same result:

_initialPos = Position;
_initialPos = new Vector2(Position.X, Position.Y);