I claim, the ornamental design for a mini game machine, as shown and described.
FIG. 1 is a perspective view of a mini game machine showing my present design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left view thereof;
FIG. 5 is a right view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view.
The broken lines showing of internal elements are for the purpose of illustrating portions of a mini game machine and form no part of the claimed design.