I haven't played enough of this game to give it a star rating, so I won't, but I wanted to use this space to ruminate a little bit on the design idea(s) behind this game -- what the ancients called "IF theory", I believe.
The idea behind "Hard Puzzle", as far as I can tell, is to generate both horror and puzzle difficulty through an atmosphere of absolute uncertainty. While the actual prose attempts at Horrifying Detail ((Spoiler - click to show)like your skin sloughing off or whatever) struck me as pretty hackneyed, you'd be shocked at how spooky it can be to have no idea how many objects are in the room, for example. The author has deliberately omitted a lot of the helpful or clarifying responses that modern Inform games typically have, and the result is something like having your eyes stricken out. Actions that provoke no response text can dramatically change what objects are available or the structure of the location. Some things are implemented in lazy ways that produce unintuitive behavior, and (maybe?) some things are implemented in a way that's designed to look like a lazy shortcut, but behaves very differently under special circumstances.
This is very spooky. The very obtuseness and inconsistency of the interaction is carefully crafted to create a sense of disorientation and dread, as you're always unsure even what *kind* of thing might happen in response to certain actions. The tone of the worldbuilding confirms that this kind of existential spookiness is the goal (even though I didn't think the worldbuilding itself was very effective at achieving that effect).
This is really interesting, and like a lot of IF experiments one of the principal questions it raises is whether this kind of thing is at all repeatable, or whether it's more of an "only works once" kind of thing (as people say of "Deadline Enchanter", say, or the (Spoiler - click to show)PC-protagonist-parser stuff in "Slouching Towards Bedlam". Certainly, I think that the effectiveness of a disorienting interface at this extreme level of minimalism is kind of a "works once" thing. But I think that, if you telegraphed correctly when it was starting, you could have (say) a spooky funhouse room in a larger game where things obey different metaphysical rules that are only conveyed to you very obtusely, by unreported changes to the world model that you have to discover accidentally or systematically (like through the use of "take all"), building towards a larger sense of horror. I think there are a lot of possibilities for this kind of thing, since there are a lot of bizarre facts about a world or location or power that a parser could strategically fail to remark upon.
One example that comes to mind of this kind of technique being employed effectively on a small scale was the game "Dinner Bell", where (famously?) (Spoiler - click to show)the PC's profound physical mutilation is only mentioned in one error message, that many players probably never see at all. Hard Puzzle is like an entire game that's trying to be scary in that way, and I think it's an interesting and clever experiment. Since I'm not much of a puzzle buff and don't have ERR:NaN hours on my hands, I'll probably never finish it, but I thought it was interesting.