Some systems, like in @CuCN's cluster, have possible inputs that can make it impossible for the player to advance as it results in a state that any input does not change the system. Adding a simple button to reset the system to the original state would allow for the player to attempt the system again without having to refresh the page.
Yeah taught well about that. Especially whem you find a sistem full of, well... data like this:
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But usually it ain't a problem. The thing is the designers made the levels like that with a purpose. To prevent mindless clicking and only allow one-chance stuff, like in real life.