Not a great puzzle, but not a bad one either.
Has anyone else used puzzles that work well in D&D or the like, especially with the combat round system? Personally, I think the best puzzles are those that combine the combat system as with the puzzle, where one or more characters have to spend their combat actions to actively solve the challenge while the others defend them against enemies that only stop when the puzzle is solved.
I designed a puzzle that worked this way for one of my boss encounters. In the centre of the boss room was a reactor, drawing power from four machines in each corner of the room. The reactor channeled power into the boss monster, giving it 5 regeneration per round per active machine. Each machine had a lever that could be pulled as a move action.
The trick was that the four levers toggled the machines active or inactive, and some would affect more than one. At the start, the first machine toggled itself, the second machine toggled itself and the one clockwise from it, the third toggled itself and two clockwise, and the fourth machine toggled all four. Each time a machine was toggled, the sequence would rotate clockwise, such that the second machine only toggled itself, the third toggled itself and one, etc.
A simple puzzle if you knew the trick, but trying to derive the pattern via observation is tricky, especially in a combat situation where other things are happening at the same time. Eventually the players decided to bypass the puzzle by just smashing the machines, which I admit is probably the best solution to that Gordian knot.
I'm always on the lookout for similar puzzles I can adapt to my games. I'm trying to invent something using number patterns like the Fibonacci sequence or so forth, but while the math is great, it's harder to game-ify it.