I really like the graphics and the sound, especially the music ^^.
Sometimes the terrain material confused me about whether the ground was walkable or not.
The extreme vignette effect when low on oxygen bothered me a bit, as I was constantly low on oxygen and never seemed to get more.
Also, I found it somewhat mismatched that the beautiful music was so calm, while the gameplay was made faster by the oxygen mechanic.
Overall, a good game that was enjoyable to play. Well done!