After hearing that this was an anime that had heavy parallels to Arrival, and watching the first five episodes, the sci-fi buff in me was ecstatic. Here was a mature, well-written and absolutely gorgeous looking and sounding sci-fi anime that was headed in a direction that didn't seem hackneyed. It was thought-provoking and sparked a lot of discussion among the viewership. It was a potential masterpiece, I thought.
But as the series progressed, anime tropes that had no business appearing in a mature narrative such as this started popping up left and right for no good reason like some rash, creating a very jarring experience, and culminating in an ending that left many wondering how something with so much potential had ended up like this. It became incoherent to the point where one has to wonder whether the author's original vision was altered by others in the creative team to appeal to a larger crowd - one that wouldn't be watching this series in the first place.
Story (3/10): The first half was a solid take on first contact, and the plot was genuinely creative and gripping at the same time. The last quarter was an unmitigated disaster for the most part. I don't think any other show with such a promising beginning has bombed so hard.
Art (8.5/10): Ah, this is something that the plot couldn't touch, and does deserve a favourable mention: the characters and several other parts are in 3DCG, and it pretty much sets an industry standard to how 3DCG should look. At no point did it look awkward or badly animated - on the contrary, some CG-heavy scenes ranged from beautiful to downright jaw-dropping.
Sound (8.5/10): Another thing the story could not completely spoil was the soundtrack, which was great. If there is one good thing that came from this show, it's that.
Character (3/10): Just like the plot, the main characters start out with great promise, but end up getting development that is frankly appalling.
Enjoyment (4/10): This reflects the effect of the ending more than anything - it leaves a very bad taste, especially because the first half was so enjoyable.
Overall - 4/10. Tl;dr: You are probably better off pretending this doesn't exist. That, unfortunately, is the right answer.