[Some spoilers ahead]
This little game is a nice journey. It's an exploration game with a bit of action. The assembly of such gfx/music (one is a slow down version of a "the fith element" melody) and gameplay makes this game unique-ish.
Unfortunately, I did discover some game mechanics when I finished the game while I decided to have a look at the steam achievements. The breeding, predator/prey law, well... I missed them totally. Some of them are insane: finish the game without being hurt is crazy, coze the movement/flapping of the bird will make it extremely hard, namely, you will need luck, a lot.
I managed to block an underwater rune with rocks... (unable to remove them to read it).
The ending is controversial: killing animals for their blood in order to power what seems a machine, is a bit too much for me. And I'm not a vegetarian person. And why pong??
The game is big enough to discourage to start again to unlock more achievements and to discover what the hell are the 2 unused triangles. I was not able to find a place where they would fit. I really did spend a lot of time looking for forgotten places in the entire world. Well... did not look hard enough... hint of the location not "strong" enough?
One bad point though: the game require the linux closed source radeon driver for full rendering. Games can be closed source, but platform (here GNU/Linux) and middleware should be open (GNU lesser GPL license protection for middleware code).