Can you add a button to reveal a hint one step at a time?
Hard optional puzzles are really hard, but I want to see how it's all solved. It also helps players from getting stuck in the main levels.
No. I've actually tested whether seeing a part of the "correct puzzle" helps people solve some of the hardest levels (e.g. Outer loop), and it doesn't - until I show practically everything. In addition to that, there are levels with thousands of correct puzzles, and some pairs of correct puzzles don't share even a single placed object (and they're not just color swaps). Then, I'd just have to pick one and promote it to the one and only intended puzzle(TM), which I don't like, because the hints would just confuse people who were on the right track, but towards a different correct puzzle.
It would be also tempting to click the button right away, so any hint system has to be approached carefully.
I'm considering having simpler versions of levels, or their parts, as hints, but often the levels in the game are already the simplest I can make them while still requiring the "idea" I want from the player but not having any alternative puzzles - it might still work, but only if I made another 50+ (100+?) "hint" puzzles and if I had some pre-placed objects in them to force the player to do what I want them to do (which I've tried to avoid due to some sort of 'puzzle purity'). Which is a lot of work, but probably very worth it.