L4608 ‘Keep Your Distance’ by Pandiculator
Posted by Encota on 12 Jun 2020
Around ten years ago my daughter made me some themed fridge magnets, in cross-stitch, which I keep on a board in my study:
And ever since 2010 I have been playing the Space Invaders soundtrack non-stop through the speakers in there – try https://en.wikipedia.org/wiki/File:Space_Invaders_Music.ogg
if you’ve momentarily forgotten that bass line.
After a year or so the sounds seemed a bit tedious but they now just seem part of the furniture. Anyway, back to this week’s puzzle …
Some relatively gentle clues gave a grid where you had to find the remainder when each pair of digits, when taken together, were divided by 25. Using A=1, B=2 etc this in turn spelt out some words of a message – an instruction + a creator. The instruction was ODD DIGITS HIGHLIGHTED. And the creator (Tomohiro) NISHIKADO. But it is easier to explain in picture form. Here is the final grid:
And here is that intermediate stage showing the letters:
What I particularly liked in this puzzle was the double-checking provided by the endgame – something one doesn’t always get from a numerical. With 58 of the 76 numbers in cells confirmed by the above letters it required only a minor bit of work to re-confirm the other 18. Using simple tests like 2 * 45 = 90, that sort of thing. I’ll look stupid now when it turns out I’ve made a mistake, won’t I!?
Cheers,
Tim / Encota
Listen With Others 
Alan B said
Tim
Thanks for the blog. I’d like to take up this bit of space to relate my own experience of this puzzle.
It is the first numerical crossword I have tried for about 40 years, not counting an interesting puzzle last year, called Well Spoken, that was a combination of a cruciverbal and a mathematical puzzle, in which numbers played only a small part.
Having got going via the bottom middle of the grid I reached nearly halfway when I mistakenly eliminated 752 (the correct answer) at H. I had to scrap my partial solution and start again. When I realised that the asterisked number (the cipher key) had to be less than 28, but not much less, I entered 752 at H and got going again.
Solving this was great fun, and I admire the ingenuity that went into the design. Clue u (68) stood out as the most useless clue I’ve seen for a long time! It was of no use at all for solving either that clue or any other, and it is itself solved only by way of clue F, which in turn is solved with the help of both S and l.
When the grid was complete, it was clear that 25 was the maximum possible divisor for the key (otherwise the sum of all the digits would be too great), and it turned out to be exactly 25, my first try. When the message was deciphered it took a few moments for me to decide that some of the letters were not significant. What was left exactly matched what the preamble said was included in it.
My rustiness showed at first, but having worked through this at the second attempt I thought this puzzle was pitched well and fairly.
It was interesting (and deliberate, of course) that only four letters in the message (a P, D, N and H) were decipherable before knowing the divisor. It was just as interesting (and deliberate) that the first five letters of the message using a divisor of 25 were PCNOD. I think it was as much by luck as anything else that I went further, and after picking up the unhelpful combination DDDD I got the real message.
Encota said
Interesting feedback – thanks Alan!
shirleycurran said
Yes, thank you Alan. It is great to learn that we are not the only ones who make a single, careless error and have to go back to the start – which usually happens with the numericals.
David Lauener said
Nice puzzle but shouldn’t there be a bar under the first digit in J across (ie the ‘3’ of 359) as there is no down clue to the crossing down light that appears as 30?
Alan B said
David @4
No bar is necessary at the place you mention. We are told in the preamble that there are ‘unclued lights’ (plural), and there are two of them, one of which starts where the J is, the other being where the asterisk is.