Keep Forking

Last week and this, I've been using my time on the bus to solve a few tactics exercises on Chess.com. I have attempted more than one hundred, finding that my concentration on the bus is often less than optimal, especially on the small screen of my phone. This afternoon, I muffed several easy ones by moving too quickly and skipping an elementary step in calculation, then spent three and a half minutes on this one.

White to move

I found the solution, then got several more correct.