I read Harmonia over a few months ago. And wow, it was a good read.
I do admit that I felt bored reading some parts of it, but that can't even compare to how bored I felt when I was reading Planetarian. With Planetarian, the inner monologue has world-building and really only 2 characters, so its a bit boring to read. With Harmonia, its more character-driven and has a variety of characters, which makes it a better read (to me personally). And the only time we ever get infodump is chapter 4 or something, when Shiona was explaining things.
Harmonia is definitely Hinoue's best in terms of art. I can't imagine how hard it may be to remember all the specific colors in the eyes to keep consistency. Her designs are also great in here. She still has the big eyes (which is her trademark) but, she put the cheeks and chin lower. This makes it look better and more mature. I can't even express the appreciation for Hinoue for doing Tipi. Her design is definitely complex. She has curly hair (which is definitely hard to draw and replicate) and she also has a loli-dress (which is also hard to draw because of all the frills).
The soundtrack was also very good. It doesn't have many memorable tracks, compared to something like Rewrite, but its only expected because Shinji and Ryo are making music that help the scenery, and not just to be remembered. I do love Towa No Hoshi E though. I think its one of the most melancholic official Key VN ED's as the ED of the main/true route. And I really do love thoseelancholic tracks, so when its the ED, its even better.
As for the story itself, it was definitely mind-blowing. Though granted, I was waiting all night for the game to load, so I played it all In one-sitting and wasn't as invested.
The only thing I still don't understand is, that it was said that Tipi was in the generation of robots where they only function with one emotion, and will break down otherwise. It didn't make sense to me, because there were multiple times where Tipi was happy when Rei was with her, yet she never broke down from that. Maybe there needs to be a certain amount of happiness, but its still interestingly flawed.
I do wish that Rei's backstory was explored more. I mean, why was he in that facility in the first place? Why did Rei have a mechanical arm (other than the obvious fact that he most likely lost of real arm)? Why did Rei wake up at that specific point in time? Why did Rei have no knowledge of his past?
and Shiona's character and back story. Why did Rei look like her brother? Is it possible Rei is her brother? Why didn't Shiona stop Rei?
And that part in the middle of one of the chapters when a human came and was badly injured. Why did he know of the song that Shiona played?
I feel like there's more connections than what is actually connected in the KN. I really do hope we get a drama CD or Light Novel like Planetarian to explain some of these aspects.
I also don't know why people can compare this to Planetarian. Sure. Robots, post apocalyptic, Kinetic. But that's it. That's like saying you can compare Kanon and Rewrite because they have girls, romance, labeled as a VN, and from Key.
The ideals from Harmonia are far different than the ones from Planetarian. I do think comparing these 2 KN's is Silly though. Harmonia will most likely reach people who didn't like Planetarian and vise versa. Just because of their different ways of storytelling and ideals.
Story - 9
Art - 10
Designs - 10
Backgrounds - 10
Music - 10
Characters - 7 (well I mean most of them are purposely like how they are, so you can't really change that).
Harmonia is a great read. I'd definitely recommend it to newcomers. It'd be an easier read than Planetarian (in my honest opinion). Planetarian will feel like a snooze fest to newcomers because of the emphasis between the only 2 characters (that possibly won't be as relatable), and the world-building.
Edit - So does anyone wonder why the OP was placed as the ED? Or why it was even energetic in the first place?