### Dr. Sudoku Prescribes #18 – Star Battle

PDF

or solve online (using our beta test of Penpa-Edit tools)

Theme: Boxed In (but it plays out differently than yesterday’s “Boxed In”)

Rules: Standard Star Battle rules. Two stars per row, column, and region.

Answer String: For each row from top to bottom, enter the number of the first column from the left where a star appears. Enter these numbers as a single string with no separators.

Time Standard: Star Battle Master = 9:00, Expert = 27:00, Novice = 1:30:00

Solution: PDF and solving video.

Editorial Note 1: Be warned — this puzzle is difficult and has inconsistent and highly variable solving times, possibly because it may require some unusual techniques. Advice on solving this puzzle has now been posted in “Ask Dr. Sudoku #3

Note 2: Follow this link for other classic Star Battles and this link for Star Battle variations. If you are new to this puzzle type, here are our easiest Star Battles to get started on. More Star Battle puzzles can be found in The Art of Puzzles, in the book Star Battle by JinHoo Ahn, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

• Para says:

4:20

I liked it, but I can understand why this could take much longer to figure out. I had the opening quickly and then it was really one key point you had to find and then a lot more deductions, but those were a lot easier. I’m not sure if I have the intended path, but what I took worked very well.

• hagriddler says:

Hmm on this one I wouldn’t qualify as novice… 🙁
Maybe it’s time for a 4th category (dummy ?) 🙂
It took me a while but I really liked it !

One (maybe obvious) hint I can give is that this would be the kind of Star Battle you could expect from someone who is called Dr. Sudoku.

• hagriddler says:

I really would like to see this one discussed in Ask Dr. Sudoku !

• muhorka says:

Good opening and nice logical deductions, which lead to an excellent puzzle! (but took me 9:11…)

• 5.17 for me. I didn’t have a pause moment fortunately, and like Bram, I can understand why the solve times would vary for this one. I’m usually not too great at Star Battle but I like the imbalance-related techniques.

• Carl W says:

1 hour, 10 minutes

I felt like I made great, steady progress for the first 15 minutes or so, (though without entering a single, definite star). Then I got stuck for a long time trying to make my next deduction. I did have at least two positions that could each only be resolved one of two ways. So guessing one of those through to a contradiction (or solution) definitely would have led to a much faster solve time.

At about 35 minutes, I was missing a single deduction that would let me wrap up the whole puzzle in a couple of minutes. But it took me over 30 more minutes to finally look in just the right place to find it.

Thanks for the tough challenge.

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