Despite the low-polygon models, Aer is a delicious-looking game. And "low" doesn't have to mean "bad", especially if those polygons are artfully placed and beautifully animated, as is the case with Forgotten Key's "sandbox" title, where the player controls a girl that can transform into a bird.
Unfortunately, right now the game is under heavy development, so we don't know exactly how it'll play. That said, Forgotten Key provides the following description on the project page:
With a focus on freedom, curiosity and aesthetics you will traverse the skies, home for nomad tribes, wildlife and secrets of old. You will soon be wrapped up in a tale of such stuff that magic is born from; prophecies, gods and dreams ... With a sandbox-like gameplay you will be allowed to explore the world as you like, and during that time help it's inhabitants. Ultimately you will challenge the gods and save reality itself.
Going by the video, you'll travel between floating islands using your shape-shifting powers and the end of the trailer hints at an underlining narrative... with darkness.
As an aside, the colour scheme and art style remind me a little of Frontier: Elite II, though its only a passing resemblance. And Frontier didn't really have a choice when it came to low-poly... everything.