Quote from KennKong on March 16, 2012, 6:02 pm

4/5. This nice little state machine falls right between sp_contaminated_area, which I dubbed "Two Gates", and Jonatan's "Seven Gates". I dub this "Three Gates"!

While I agree with other posters' comments about indicators, especially for the exit, I didn't have any trouble figuring out what did what. I don't agree with any who complain about the possibility of getting stuck. I think one would have to do something deliberately stupid (is that an oxymoron?) to get stuck.

The puzzle is good enough to rate a 4, and the slight visual shortcomings aren't enough to drag it down to a 3, as it barely qualifies as "needs work."