Outstanding! Very nicely plotted. A good little nostalgia trip with decent graphics and scenic music and sound. I liked the self-awareness and touches of humor. It's worth replaying to get all three endings, they are quite distinct! The real trick is finding both the "cheating" and "beating" methods of solving each puzzle.
A bit of a shame about the lack of voice-acting, though I suppose the cheapness was part of the charm. Voice acting can add a lot to the atmosphere of a game if done well (Beneath a Steel Sky springs to mind, in this genre).
My major reservations? Dialogue, though witty, goes on too long, and there is no way to skip through the reams of dialogue (particularly in the first room) when you replay. More complexity to the tasks might have been nice but then it would have been a longer game (I quite like a good minigame puzzle and this game didn't really have any). There were few interactable elements in any scene - a nice escape from pixel hunting, but I quite enjoy clicking on random objects or places and getting a wry description even if I can't use the thing. A little more of that descriptive dialogue wouldn't have gone amiss.
Nothing that would make me give less than five stars though. Top stuff.