Very nice trick. I pretty quickly identified what needed to be done, but it took me a few attempts to actually put it into practice the right way. It’s amazing how many moves it saves over a naive solution, though.
I struggle at this level since always... Can't even reach a 2 off. Pipelining is something I can't seem to learn: I know some of the famous tricks, but each new board is a new challenge and what I know doesn't help me. It's demotivating at times... :(