SEIF 1 (Cont.)
The Rambam and Rosh holds that the Gemara stated that the only problem is going from room to room. This implies that moving from one side of the room to another is not a problem.  The Rif says that you cannot even shift from one side of the room to another. He says the proof is that the Gemara does not allow going from one floor to the next.

The Ran explains this proof, saying that the Gemara is not exact when referring to moving from one house to another. So once we understand that the Gemara is not exact, we can assume changing from any place would be included in this Halacha, even from one corner of a room to another.

The Maged Mishna says that the Rif agrees with the Rambam that there is no problem moving around within a room. When he says that "from one side to another not," he does not mean it is prohibited, but rather that it is not included in the problem of changing places.