The premise of the puzzle is that each cube has a mix of one of four icons on each face. Your goal is to stack these four cubes vertically so that each face that is showing a different face (four faces showing per cube as you can't see the top or bottom face). As I mentioned in yesterday's post, it's much like Sudoku where each line has to have something different.
Apparently this is all based on the Polya Enumeration Theorem. I haven't had to time to actually read this article, but it explains how one create their own with different patterns on the cubes.
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