Happy Friday! If you're new to Now I Know, you'll notice that today's format differs from the rest of the week. On Fridays, I pause to write the "Weekender," my "week in review" type of thing, or to share something else I think you may find interesting. Thanks for reading! — Dan
Two Very Fun, But Very Hard, Sudokus
Hi!
If you’ve been reading Now I Know for a long time now, you know that I like variant sudoku puzzles. If you don’t know what sudoku is, start here. I’m going to assume you’re well past that point, because you’ll have to be in order to do the second puzzle I’m going to share momentarily. That puzzle (you’ll see) is a variant on the traditional sudoku rules. The normal rules apply — you can only put the numbers 1 through 9 in the grid, and you can only have one of each digit in each row, column, or 3×3 box. Variant sudokus have all sorts of weird rules in addition to that — ones that require a little bit of arithmetic and logic that normally wouldn’t apply.
But first, let’s start with a normal sudoku — probably the hardest one I’ve ever done. I found it via Cracking the Cryptic, a sudoku puzzle YouTube channel I’ve mentioned here a few times. You can watch the channel’s co-host solve the puzzle here, but try it yourself, first — you can try the puzzle online here. (You can print this one out and still do it, if you prefer. The same won’t be true for the second one I’m sharing today.)
I won’t share how to do it — the Cracking the Cryptic video does a better job than I could have.
But that’s not the real gem of the day. The puzzle below, via James Sinclair’s newsletter Artisanal Sudoku, is incredible. If you click that link, you’ll first get two other variant sudokus that are much, much easier (but still fun) — the first one is a breeze, and a good way to understand how variants work. (Hint: you can’t put a 5 on a V or an X, which makes the longer thermometer very, very straightforward.) His newsletter is a fantastic source of variant sudokus of all difficulty levels, and the third one he shared this week was so good, I couldn’t help but share it.
First, the rules:
1) Normal sudoku rules apply: fill each row, column, and 3x3 box with the digits 1-9 once each)
2) Dynamic fog: correctly placed digits clear fog from their own cell and possibly other cells.
3) Cages: the sum of the digits inside each cage is equal to the small number in the top left corner, and digits cannot repeat within a cage. All cage sums are given.
4) Arrows: the sum of the digits along an arrow is equal to the digit in the connected circle, and these digits can repeat if allowed by other rules. Arrows do not cross or overlap, and all arrow sums are single-digit.
James has a quick explanation for how cages work in fog puzzles in this week’s newsletter — click here for that — in case the above is ambiguous.
Now, the grid — and you won’t see much!
Yes, that’s solvable! It took me a few hours on and off over a couple of days, but I was able complete it. And it was so much fun, I did it again afterward, just to make sure I understood the logic — and still got stuck at some points!
Give it a try and if you get stuck and want some help, take a screenshot and send it back to me — I’m glad to help. (I’ll try to check my Now I Know inbox more often this weekend!)
Have fun!
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The Now I Know Week In Review
Monday: The Burger With a Side of Insensitivity: It’s hard to make an offensive hamburger, and yet…
Tuesday: When the Klan Got Kicked Out of Town: I’ve been meaning to share this story for a while; I’m glad I finally got around to it.
Wednesday: How to Fly With a Cello: It rides next to you, typically. And often in business class or better.
Thursday: Getting Divorced Over an Illegal Hyphen?: Reader Stephen M. pointed out that there’s no actual hyphen mentioned in the story, which was a miss in my part. I was referring to hyphenated last names (e.g., “Day-Lewis”) which typically (but amazingly, not in the case of Daniel Day-Lewis) reflect a husband and wife combining their two last names into one.
Long Reads and Other Things
Here are a few things you may want to check out over the weekend. And apologies in advance if you suggested one of these and I failed to thank you — I lost my notes on how I found some of these.
1) “How a fake astronaut fooled the world, broke women's hearts, and landed in jail” (Space, 27 minutes, June 2025). The subhead: “For years, Robert Hunt convinced everyone he could that he was a NASA astronaut. The truth was anything but.”
2) “A history of pizza” (Histories of Things, 10 minutes, June 2025). It’s a history of pizza, as promised by the title.
3) “The radical 1960s schools experiment that created a whole new alphabet – and left thousands of children unable to spell” (The Guardian, 11 minutes, July 6). The subhead: “Decades ago, a generation of UK schoolchildren unwittingly took part in an initiative aimed at boosting reading skills – with lasting consequences.”
Have a great weekend!
Dan