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I really like the way this gives immediate feedback to the designer. It might not be the best way to actually design a well-crafted puzzle, but you can just adjust the variables around bit by bit and instantly know if you've destroyed the intended path through the puzzle or opened up a bunch of unintended ones.

I've never been able to find the video of the talk since I watched it originally, but I remember Marc Ten Bosch (Meigakure dev) talking a bit about state spaces and how he tries to design puzzles that create large state spaces with a short goal path, the notion being that these puzzles are easy to solve, but only if you know the solution. This kind of visualization would be pretty useful if that's your design philosophy, especially if it was integrated right into your dev tools (assuming your game lends itself well to being analyzed as a state space - grid based movement and all that).