Well that's forty-seven down...

I finished off the almost all the single layer achievements, and for the most part they are related to neat Easter eggs that I missed the first time through. Things like what happens if you walk into GlaDos and Wheatly's obvious death traps, a painting of the CEO's assistant that made up part of GlaDos' AI, and the last location of a ship that was reported missing in Half-Life 2.

The co-op was interesting, but it's awkward running at the pace of some stranger, so I didn't play it much. If I get a second controller I might run it split screen myself just to see what the rest of the levels are like.

Then I ran through the whole single player game again with the cometary track bubble on, and since I already knew how to solve the puzzles it took MUCH less time.

Tomorrow it's on to Final Fantasy XIII, with nicer visual, weaker writing, and much less game play.