I claim the ornamental design for a board game, as shown and described.
FIG. 1 is a perspective view of a board game, showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a left-side elevational view thereof, the right-side elevational view being a mirror image thereof; and,
FIG. 4 is a front elevational view thereof, the rear elevational view being a mirror image thereof.
The broken lines showing a die and marble tokens in FIG. 1 depict environmental matter and form no part of the claimed design. The shading lines depicted in the recesses in the top of the board depict contrasting colors. The bottom plan view forms no part of the claimed design.