Just finished this Friday’s Listener puzzle, “Heart”. Whew. It’s essentially a diagramless crossword, with some additional quirks that have to be discovered. The clues are given in the correct order but with no other information, not even where the across clues end and the down clues begin. We’re told that the grid has 180-degree symmetry, though, which turned out to be very helpful.
At first the thing looked just about impossible, and by Friday night I had solved only 12 of the 42 clues and had put nothing into the grid. I didn’t get much puzzle time in on Saturday, but this morning I figured out where the break was between the acrosses and downs, which helped me make it to maybe 17 or 18 answers. At that point I found four answers that could plausibly interlock, and solving got much easier after that. There are some further instructions to apply to the filled-in grid in order to get the final grid, but they didn’t take me long — the difficulty in this puzzle was all at the beginning.