Goldilocks Sudoku

This is the Goldilock's puzzle. It has 3 solutions. The first and easiest solution is found after placing a 1 in the central gray box. Placing a 2 in the box gives a moderately difficult solve. Placing a 3 in the central box gives a difficult solve.

Rules:

After placing your chosen number in the central box, normal sudoku rules apply.

Enjoy!

try it here or watch a solve from Mark Goodliffe here