### Star Duel by Carl Worth

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Theme: A Star Battle

Author/Opus: This is the 2nd puzzle from guest contributor Carl Worth.

Rules: Standard Star Battle rules with three stars per region. Also, both grids will have the same position of stars. The shading is for aesthetic purposes only.

Answer String: For one of the grids, for each row from top to bottom, enter the number of the column where the middle star appears. Enter just the last digit of any two-digit numbers, and enter all these numbers as a single string with no separators.

Time Standards (highlight to view): Grandmaster = 9:30, Master = 18:30, Expert = 37:00

Solution: PDF

Note: Follow this link for other variations on Star Battle and this link for classic Star Battles. If you are new to this puzzle type, here are our easiest Star Battles to get started on.

• Paul K says:

Nice smooth solve for the puzzle. Had all kinds of brain fades on entering the answer string.

• Carl W says:

Thanks, Paul. The shapes I was going for required a fairly large grid. Hopefully it wasn’t too tedious going back and for with all the notation.

• hagriddler says:

That was fun ! Relative smooth solve, meaning for three cells I had to prove if they could/should contain a star.
I would like to know if it’s possible to solve without such logic. I used : ebj ryrira/pby gjb, ebj svir/pby ryrira, ebj fvk/pby guvegrra

• Carl W says:

I’m glad you liked it! If you’re asking if any guessing is required, then, no, a logical solution without guessing is possible. One of the cells you asked about can be determined from the opening of the puzzle:

Fcrpvsvpnyyl, ebj svir/pby ryrira. Pbafvqre gur gjb funcrf fcvenyyvat nebhaq rnpu bgure ng gur gbc bs tevq gjb. Va gur fznyyre fcveny, gjb fgnef ner vzzrqvngryl qrgrezvarq, (ebjf bar naq guerr bs pbyhza gra). Guvf yrnirf bayl gjb cbffvoyr pryyf sbe gur guveq fgne va gung ertvba. Gura, guvf guveq fgne, (juvpurire ybpngvba vg gnxrf), jvyy fgrny gjb pryyf sebz gur bgure ertvba, (pbyhzaf frira naq rvtug bs rvgure ebj bar be ebj sbhe). Gung sbeprf gur fgne va ebj svir/pby ryrira.

For the other two cells, they are determined much later in the puzzle, so I won’t describe everything about how to determine them, but just the last step before each (in my solving path at least):

Sbe ebj ryrira/pby gjb, V svyyrq ebj ryrira va tevq gjb jura n fgne jnf sbeprq vagb ebj ryrira/pby frira gb pbzcyrgr gur evat-funcrq ertvba.

Sbe ebj fvk/pby guvegrra, V svyyrq pbyhza ryrira juvpu sbeprq gjb cbgragvny fgnef va ebjff frira naq avar bhg bs pbyhza ryrira naq vagb pbyhza gjryir. Bar bs gurfr gura ceriragf nal fgneg ng ebj fvk/pby guvegrra.

Thanks again for trying my puzzles!

• James McGowan says:

Excellent theme! I know sudokus can sometimes have ‘X-wings’ in them, but this is far better 😀

• skynet says:

2hours 13m…Dreary and such difficult logic.Can’t say I really enjoyed it….The huge amount of time took a lot of the experience away.Guessed to the solution after beginning to feel tired scouting for the logic …..ufff

• skynet says:

Never mind my time.I have a broken puzzle.

• SergeyS says:

Thanks for this puzzle! I almost solved it looking at only first grid 🙂 Then I realized it is allowed to look into second one too. Tough one though.

• Carl W says:

You’re quite welcome. And thanks for giving it a try.

I never attempted solving either grid independently, but by just looking at the solution, it’s fairly straightforward to determine that neither grid alone gives a unique solution. So, for your sake, I’m glad you finally started using both grids together.

Happy puzzling!

• SS says:

A wonderful concept for a puzzle. I wish that this wasn’t the only one of its type on here! 🙁

• Carl W says:

Thanks! I’m glad you enjoyed this.

As for more puzzles of this type, you can look at the 2016 US Puzzle Championship (http://wpc.puzzles.com/uspc2016/) where I have a pair of USPC-themed grids with the same rules (going by the name of Star Battle Twins). A (free) registration is required to download the puzzles.

I have a second Star Battle Twins puzzle there as well. It’s given as the example puzzle in the rules, but it’s a full-size 10×10 grid with a spiral/zig-zag theme that I am quite pleased with. I think it demonstrates the aesthetics that are possible when spreading constraints across two grids simultaneously.

So to solve that second one you’ll have to be careful to not see the solution that’s printed right next to it.

Thomas, maybe that spiral/zig-zag puzzle could be run in its own right here on this site sometime? I feel like it got a bit wasted just as the example for the rules, (it’s probably rarely ever been solved by anyone).

• Julius Jacobsen says:

I’ve stared at this for 45 minutes before realizing that this is a 3 stars per region puzzle, not 2.

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