Stackable cube puzzle

FIG. 1 is an isometric view of the stackable puzzle cube showing our new design in its assembled state;

FIGS. 2-6 are isometric views showing each of the five middle sections of the puzzle;

FIG. 7 is an isometric view showing the top piece of the puzzle, rotated 90° clockwise from FIG. 1 ; and,

FIG. 8 is an isometric view showing the bottom piece of the puzzle.

The dashed lines shown in FIGS. 2-6 are included for the purpose of illustrating portions of the stackable cube puzzle that form no part of the claimed design.