I just experienced Proteus, and in a word it is: wonderful. I say "experienced" because this definitely is
not a game in any sense of the word; and you really have to get out of that gaming mindset to enjoy it. I had heard that it was an "abstract game" but I wouldn't even say that, it's certainly abstract but not a game.
I have to admit that it took me a good thirty minutes or more to start appreciating it fully. I started off intrigued, looking around and exploring, but after walking around a bit I was thinking "Okay this is interesting but what do I do now?", I was starting to get bored and frustrated. I felt an uneasy sense of detachment that came from the lack of interaction with objects in the world, sure some creatures run away when you chase them but that's about as much recognition of your presence as you'll get. I felt like a ghost.
Then I came to the top of a hill and I stopped... I
stopped, I looked around and I listened. I sat down on the top of that hill (yes there is a sit button) and watched the clouds grow near until they were over my head and all around me and it started to rain. Each drop of rain played part of a tune that was going on all around me, and then I realised that these ambient sounds were not random noises, everything in the world was singing: every tree and bush and creature, every hill and mountain, the sea, the sun, the stars, the wind, the rain and the snow, the day and the night. Every particle of the world was singing in harmony and the players changed as I stood up and moved over the land once more.
I stopped thinking about what I should do or where I should go, I did not care for moving or doing anything at all, I only moved on when I grew tired of a particular sound or glimpsed some far off place and wondered what it sounded/felt like over there.
I think this might be something I come back to when I'm feeling stressed out. I don't think I've experienced anything so relaxing in my life. I'm really surprised that Proteus totally blew me away, I was expecting a nice little interesting world that I'd look at for a few minutes and then never touch again, and I still felt that way for at least quarter of an hour in, I'm glad I stuck at it and honestly feel a little embarrassed for being so slow on the uptake.
The difficulty in learning is not acquiring new knowledge but relinquishing the old.