Brilliance as usual
I always look forward to the Submachines - they generally kick ass. This is no exception. The sound creates the perfect atmosphere to suck you right in, and there are plenty conundrums to confuse you without being cheap or frustrating.
Only minor letdown (MINOR SPOILER AHEAD) was the ending - a little TOO much Half Life going on there. That said, it didn't detract from my enjoyment of the game.
Overall, awesome stuff. I tell you what, you should do a collaboration with the guy who makes the 'Gateway' flash puzzlers. The potential for awesomeness there is massive.