I have a very similar story to RMKelly. I tried this earlier this year and was stuck 2-off, but coming back today I solved it pretty much immediately! Glad to have finally extracted the vanilla. Cool level and nice solution!
Wow, I remember having trouble with this when I last played it in February, but I got it in my first try today! Lucky me. Its always interesting to see the creativity used with a width of the 3.
I don't understand how a 3 column level manages to have this many possible options, and still manages to hide a crucial concept behind everything. One of the best levels in the game, but it is very very hard.