What is the measured difficulty?

Every puzzle gets a difficulty score measured from the finished grid (how the words run, how many go backwards, how much they overlap, how well the filling letters hide them). The difficulty curve at the bottom of the studio shows every puzzle's measured level against the level planned for its place in the book, with a summary such as "37 of 42 at their planned level". A small ring above a bar (shown as "Off plan" in the legend) means a puzzle measured easier or harder than planned. Click it to open the puzzle, then try "New puzzle" or move it.