Star Battle: Pentominoes, and Pentominous: F is for Fiendish

I just had my fifth puzzle published at GM Puzzles.

This was a fun one. It's my second Star Battle puzzle, and it's definitely more approachable than my previous dual-grid Star Duel. (Incidentally, that giant Star Duel was noted as one among several of the best object-placement puzzles of 2014 at GM Puzzles. I'm happy to see that people liked it.)

I got the idea for today's Star Battle when reading that best-of post. One of the other puzzles noted there was this lovely 9-pentomino Star Battle by Zoltán Horváth. The post mentioned that another designer, Jiří Hrdina, had independently designed a similar 9-pentomino Star Battle. (I can't link directly to that one since it's not freely available on the web. It's contained in The Art of Puzzles: Star Battle e-book available for sale). Then, in the comments, Matúš Demiger mentioned that he had also independently constructed a third 9-pentomino Star Battle as part of the 2014 24-Hour Puzzle Competition.

So at least three puzzle authors all happened to construct pentomino-themed Star Battle puzzles last year, and all three happened to choose the fairly-standard 10x10 grid size, (forcing the puzzle to include only 9 of the 12 possible pentomino shapes). Matúš's comment was "I hope someone will try to include all twelve pentominoes" and I couldn't resist the challenge.

And it was an interesting challenge since putting 12 pentominoes into a Star Battle requires a 13x13 grid. That's not too much of a problem in and of itself, (my Star Duel used a 15x15 grid, for example). But with this particular theme, as the puzzle grows the total area of the pentominoes grows linearly, while the total puzzle area grows quadratically. In my final puzzle there are 12 regions of size 5 and then one giant outer region with 109 cells. But all 13 regions each only contain two stars. So the real challenge here was to ensure that when solving the puzzle the stars in the huge region didn't get determined early, (causing a bunch of cells to be wasted and forcing the user to tediously mark off all of the unused cells).

Luckily, I think it just worked out. In all of my test-solving, the stars in the large region are among the very last determined.

Anyway, give this puzzle a try if you'd like. The large number of tiny regions means there are a lot of easy steps early on in the puzzle. But there are still a few more interesting deductions in store later on, (but nothing ever all that difficult in this Wednesday-level puzzle).

I should also thank Thomas Snyder for his editorial help. He found and fixed a small ambiguity in the first version of this puzzle that I submitted. I've since coded up a deductive Star Battle solver just to be able to verify uniqueness for puzzles I construct. But maybe I'll talk about that in a future post.

PS. If anyone is following closely, I neglected to mention my fourth puzzle when it was published a few weeks ago on a Friday. It's a Pentominous puzzle with almost no clues other than 12 F's, and I named it "F is for Fiendish". The title is a warning, and I think it deserves it. I think this is the hardest puzzle I've published so far. My Star Duel earned a longer estimated "Expert" time, (37 minutes compared to 20 minutes for "F is for Fiendish"), but that's mostly because Star Duel is so much bigger, (2 15x15 grids compared to a single 10x10 grid). The deductions required here are definitely harder to find.

My sister is really kind to do some of the initial testing of several of my puzzles. After I handed her a copy of "F is for Fiendish" one evening, she called me later that night to ask, "Can you email me a fresh copy of that puzzle? My husband and I have been trying it over and over and the paper is all disintegrating after so much erasing." That's a beautiful thing for a puzzle designer to hear---that someone is terribly frustrated with a puzzle, but still determined to stick with it and keep trying.

So if you want a challenge, give "F is for Fiendish" a try. There are logical steps that can be found at every point to solve the puzzle without needing any guessing or back-tracking, (but they may not be easy to find). Good luck, and happy puzzling!