### Championship Chatter – Which Came First: the Arrow or the Thermo?

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This puzzle was inspired by a comment I read somewhere of someone stumbling on a Thermo-Sudoku by solving it for awhile as an Arrow (or vice-versa, I can’t remember exactly). The goal was simple: can I make one puzzle that solves both ways depending on the type of shape placed into the grid. The theme here speaks mostly for itself.

But if you want an extra challenge I’d recommend solving from these images (Arrow / Thermo) or PDFs (Arrow / Thermo) which contain the original draft of the finished puzzle. The arrow is probably a much better challenge as a result, but the Thermo is at the very high end of the difficulty scale and better for a slow solve than a competition solve. Fortunately there were a good set of symmetric positions that still matched with digits so I could add clues to both puzzles without spoiling the theme. Of course, almost all the remaining digits differ but I guess that is the point.

Some people have asked about the construction steps to get two working puzzles of very different types. I normally design both of these styles by hand starting from an image of the shapes and then slowly adding digits. Here I simply did this at the same time for two different styles. The intention of having the centers work quite differently in the two types made the first four givens in the center the start. The 1’s in the corners were also great clue digits for both Arrow and Thermo types for different reasons. As I got some other good logical placements worked out, I did use some software tools to confirm each puzzle still had possible solutions before going too far down a dead-end. Gradually a duplicated puzzle came into form.

Enjoy what were probably my favorite puzzles from the USSQT.

PDF

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

Theme: Deja vu

Rules: Standard Arrow Sudoku rules.

Answer String: For the USSQT, the answer strings were a set of rows/columns encountered late in the puzzle. For this week, you can just hit the solved button on an honor system if you think you’ve solved it.

Solution: PDF

PDF

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

Theme: Deja vu

Rules: Standard Thermo-Sudoku rules.

Answer String: For the USSQT, the answer strings were a set of rows/columns encountered late in the puzzle. For this week, you can just hit the solved button on an honor system if you think you’ve solved it.

Solution: PDF

• Wow, I hadn’t even noticed that in the heat of solving. I’m glad I read this and saw the impressive design here! They were fun puzzles even without knowing this amazing extra constraint.

• hagriddler says:

Silly me, I thought for a moment both puzzles required the same solution… Nice one (or two actually) !

• Figonometry says:

It may have been me: http://motris.livejournal.com/157983.html

Well done making it work!

• Aaron Chan says:

The originals (without the extra digits) were indeed quite nasty. Took me hours to get the thermo right.

• drsudoku says:

Yep. I believe there are just the two paths I was looking at when making it to get early digits into the grid, and because I was working for two puzzles I wasn’t necessarily intending this to be the break-in but did want it available later.

One is along the lower-right thermo that goes up and you can place a 4 and 5 in the second/third cells easily and with more work get some extras in column eight — the 9 and 6 certainly. The other is dealing with all of the fifth column. First where the 3 goes, then realizing how R267C5 will fill all of 789 making R8C5 into a 6. I never found anything else to do in my testing until I worked out both of those things.

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