The art is clean and very realistic, especially for the characters. As for the designs of the mechs... eh, they are not the norm and you really need to look at them with an open mind ha ha. The animation is also very good but don't expect highly choreographed mech-on-mech fight scenes because it's not really that type of show. Most of the battles are handled by light beams and expanding energy auras, probably done partly for the story and partly to save cost.
The English voice acting is very good and has different accents for characters from different countries, something which is lost in the original Japanese. There is a trio of characters with heavy German (?) accents that that speak in a rhymey way that is pretty hard to understand if you don't have closed captioning and that in itself almost derailed the show for me. The music during the show is not that memorable but the ending credit songs are great! Unlike most anime, each episode ending is unique and has a different vocal song sung by the female Japanese lead. And you can actually purchase albums of the full 13 songs! As for the art and animation of the end credits, it's mainly a stylistic and recolored mix of scenes or sub-elements from the episode but put together in interesting and sometimes unexpected ways... like a music video. I quite enjoyed them.
And now to an important detail: the story. As I said earlier, the art is realistic and they may make you come into the show expecting realism, but that kind of attitude may get in way of you enjoying the show. For example, a show like Kill la Kill has some pretty unrealistic art and so your mind is conditioned expect weirdness from the story. This show is not as silly but the story is kind of meta, almost as if the universe of the show was created by a god based on a single theme. There is no breaking of fourth-walls, so the show is realistic in the perspective of it's own universe and theme. The pacing of the story is a bit rushed as they try to squeeze a potentially grand story into just 12 episodes. That usually happens in the last few episodes as the story becomes more important than the characters. I do wish there were more episodes to flesh out the characters and their relationships.
The dialog can sometimes be annoying because just when you expect them to explain something or say something important, they say something meta. In actuality, the characters may speak parts of song lyrics, most of which are from older rock songs. Likely if you know those lyrics, the dialog may actually have more impact. Perhaps this is another aspect that is weaker or lost if you watch it in Japanese. The lyrics could be thought have as rock-and-roll-related Easter eggs for those in the know, and the same can be said of other elements like character names and the way they look.
It's normal to start watching a show with your mind racing to try to find similarities to other shows or media. The music theme made me think of Heavy Metal and The World Ends With You. The journey of the boy and girl through a post-apocalyptic world made me think of Eureka or Heavenly Delusion. At some point, you have to just relax a bit and enjoy this brief ride.
