I've gotten a decent ways into it, but the game gives me serious motion sickness in the dark rooms. It's really hard to get your bearings in the completely dark rooms when you're looking around, and after only 20 minutes I was feeling bad enough where I had to stop playing.
It's a neat game though. I like it more than Portal in some senses since it's more simple and intuitive, though that might also turn people off. Nothing has been difficult too far, but I'm also not even at the halfway point so I don't think I can make too many judgments. Dunno if I can finish it with the motion sickness stuff though.
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No amount of planning will ever replace dumb luck.