This is my First Circle. Over the past six days, I've blasted through all of the Level 10s through the Level 30s. I was surprised at how many of them I recognized from my attempt last May to complete the 7cir program. (Not that the solutions popped out immediately, but I got this "I've seen this before" feeling, and it didn't take long to find the solutions.)
Most of the problems were pretty straightforward. A few, however, have inspired hour-long exhaustive explorations into the reasons behind every variation, especially logical-looking defensive moves that the opponent did NOT play.
For example, the next one I need to work on before I move on to the Level 40s is the following sacrifice by Tal:
Question Number One for me will be: Why is 1.Rxf6 superior to Nxf6? "Positionally" speaking, I know that the Queen and Knight work well together, as their moves complement one another, although concretely speaking, I will certainly need an answer like "the knight needs to remain there to guard the crucial c5 and d6 squares."
[Edit: Immediately after posting this, I saw that 1.Rxf6 threatens (say, after 1....axb3?) 2.Rxg5+ Nxg5 3.Qxg5+ Kh8 4.Qxh6+ Kg8, though this may not be best for White.]
It seems that the "real" tactical program has for me begun tonight, now that I am encountering problems in which these analyses are helpful.