Each square in a $5\times 5$ grid is either filled or empty, and has up to eight adjacent neighboring squares, where neighboring squares share either a side or a corner. The grid is transformed by the following rules:

• Any filled square with three or four filled neighbors remains filled.
• Any empty square with exactly four filled neighbors becomes a filled square.
• All other squares remain empty or become empty.

A sample transformation is shown in the figure below.

Suppose the $5\times 5$ grid has a border of empty squares surrounding a $3\times 3$ subgrid. How many initial configurations will lead to a transformed grid consisting of a single filled square in the center after a single transformation? (Rotations and reflections of the same configuration are considered different.)