Boo makes no reaction to the game. ^ ok he does make a reaction he finds it rather funny evidence: in the end of ch 4, scout hears laughter coming inside the radleys.
The boo radley game is a game when Jem, Dill, and Scout pretend to be the Radley's. Scout is Mrs. Radley and she sweeps the porch, Jem walks up and down the front lawn and Dill is under the porch and...
It was when Dill, Scout and Jem would act out the stories they heard about Boo Radley. It was a mostly fictional game since there was no proof what so ever that what they were acting out really...