Knights of Sidonia, based on the Japanese manga of the same name by Tsutomu Nihei, is a CGI anime available for streaming from Netflix. It tells the story of Nagate Tanikaze, a mysterious young man raised by his grandfather in the "underground" levels of a massive space station. With a mastery of piloting granted by spending his entire life training in a simulator, he joins the military to pilot mechs called Gardes in an ongoing defense effort to defend the space station, Sidonia, from the bio-technological aliens known as Gauna. Little is known of the creatures, except that they destroyed Earth centuries ago and have been pursuing the remnants of humanity across the stars.
Knights of Sidonia is, in broad terms, something of a mix between Neon Genesis Evangelion and Attack on Titan. It follows a contained population as elite warriors protect civilization from mysterious beings attempting to breach their defenses. These beings have one very specific weakness that the warriors exploit to kill them. I cut the show a bit of slack since it was actually written around the same time as Attack on Titan, so I bring up the similarity less as a criticism and more as a sales pitch. The structure of the first season reminds me of the early episodes of Evangelion, where we see the alien threat in multiple different forms and explore what the creatures might be capable of.
There are a lot of things I liked about this show. I was turned off at first because it was 3D instead of more traditional 2D, but by the end of the season I didn't even care. The design of the world and the things in it is really interesting an unique. The Gauna are grotesque, fleshy monsters that morph and twist their flesh to adapt to new combat situations, and as someone who still like the Yuuzhan Vong, bio-ships will always get my attention. The setting involves all sorts of interesting bits and bobs you wouldn't hear about in most shows--emergency protocols and pieces of technology are given just the right amount of explanation.
The show features the Big Eater Anime Hero cliche, but actually manages to somewhat justify it. In this future world, all humans are genetically modified to be able to photosynthesize. This means they only have to eat once a week. But, having been raised under mysterious circumstances (And for other, spoilery reasons), Nagate can't photosynthesize. To the viewer, he eats a totally normal amount of food, but in-universe, he eats three weeks' worth of food a day.
The show teases some questions about identity: an alien attempts to form itself a human body to imitate its captors and communicate, one of the main characters is genderqueer, an old war criminal is replaced by a clone while the original body is kept in stasis so they can occasionally mine its brain for information. These questions never really pay off. Perhaps they are addressed further in Season 2, but as of the end of the first season, they're little more than set dressing. In fact, other than being one of three or so prospective love interests, the genderqueer character mentioned above doesn't really accomplish anything on their own or indeed seem to matter much outside of occasionally reminding the viewer that other, nonbinary genders exist...yet, again, there's no payoff. That's not really a theme that gets explored, they seem to exist just to constantly get misgendered and pine for the hero. You have to do more with the character than nothing at all.
A surprising arc to me was an early trio of episodes that depict the main hero and one of his several (approaching harem level, really) love interests stuck in the cockpit of a mech with no power. They live off of rations and emergency supplies for three weeks and grow very close in this time, and it's the first time we see Nagate really bond with someone. I had expected nothing but shooting and explosions and fighting, so it was a welcome change of pace to slow down and just think about space for a while.
My last point is another low one: The pacing is brisk to a fault. Outside of the above mini-arc, characters rarely get time to absorb and process the revelations of the plot as they occur. As a result, the show begins to give itself an urgency and a tension that it really hasn't earned. It establishes two rivals for the hero to butt heads with, but instead of letting those conflicts happen, those characters are either killed off or slowly hedged out of the plot to become excuses for technobabble and exposition. If you watch the show in large chunks, you may not notice these hiccups, but when you look back, you'll find plenty of questions about why characters just accepted the events of the show and moved on without any question.
I hope I don't sound too dour. I do like the show and I'll watch the second season. I think I'm mostly upset at how it gets so close to being great but falls just short, mainly due to the pacing more than anything else. But if you like cool mechs and fighting monsters in space, you could do a lot worse than Knights of Sidonia.