I'm now through 7 levels, and know where 8 and 9 are (though I'm missing a HC).

One unfortunate mistake: the 'puzzle' room in Level 7 is broken, it that a block cannot be pushed 'off the path' (which causes it to become immobile in Level 5, as it should). As such, I was able to just keep pushing the block back-and-forth without needing the clue room (which I came across later). A novel idea, nonetheless, and an error that can easily be fixed.