Even in its current state, this is already the best game of DD64 (and of DD50 and DD52). Mostly just needs to fix the visual bugs already mentioned in other comments.
For more abstract higher level feedback, it can get mentally exhausting after a while going through puzzle after puzzle. Maybe there might be a way to pace things somehow with more breather areas or ways to teleport between puzzles, because my current coping strategy to getting tired is to outright stop playing and come back later, which probably isn't ideal.
And not to put too much pressure on the writer, but figuring out the right lore for the game could potentially mean the difference of whether this turns out to be "just" a great game to an all time classic.