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Hmmm. I'm stuck in a puzzle that I suspect has some more of those hidden URs like the last one. Can anyone help?

+--------------+--------------+---------------+
| 89 89 5 | 167 167 2 | ...

Thanks, Marty, and all. That makes sense.

Are you familiar with Hidden URs? One on the 25 UR will remove the 5 from r8c7, exposing a Type 4 UR on 27.

Thank you! That solved it. I am familiar with URs, but I don't quite understand the &qu ...

Look for a quad in row 9.

Aha. The quad also exposes a hidden pair (R9C47) of "25"s. That solves R8C1 (1) and eliminates 4 from R8C3.

Thanks so far... still looking for the next st ...

Indeed, that helped a great deal! Thank you! Now, the puzzle is at this position:

+--------------+------------+-------------+
| 5 146 149 | 79 14 2 | 3 467 8 |
| 3 7 169 | 8 ...

Thanks to your help, I've been able to use some of my newly learned techniques to solve more and more of the "fiendish" puzzles I encounter. However, I am stuck again on one:

+-------- ...

Thanks everyone. The first response helped me solve the puzzle. I was confused by the talk of R7C7 being a naked single when it was not only already a solved cell but was one of the "original&q ...

The Draw/Play generator rated this as "too hard". It's rated as "fiendish" on my smartphone software, but the last 5 puzzles from there that I have "drawn" on this site ...

gary, no need for wing and chain moves - look for colouring/turbot.
hint ..

Yes!! That did it! After your hint, the eliminations exposed another skyscraper (that's what I usually cal them) on th ...

Hmmm. I ran into a wall on this one. No wings that I can find (X, XY, XYZ, or W), and my chains all wind up at inconclusive dead ends.

+--------------+-----------------+---------------+
| 137 23 ...

Once again, WOW. And, thanks to all of you for helping with this.

Oops... I spotted it. Partially hidden quad in box 8.

Also: how did you solve the 7 in R9C1? I don't see it.

Kieth:

You actually have some additional 9's that I've already eliminated. There is an X-wing on 9s in R2C15, R7C15, eliminating the 9s from cells R3C1 and R3C5 and R8C1.

Gary, it looks to me like a whole bunch of basics not done??
For a start you have r8c5=752 yet there is a 2 solved in c5 and a 7 solved in r8.

oops

The cell in question was entered incorrectly ...

Last time I posted a puzzle on which I was stuck, the solution ended up being a couple of (rather long) chains. I have since done much practicing in that regard and have found it to be quite a satisf ...

Is anyone aware of a puzzle that cannot be solved using just basic logic, x wings and xy wings?

In general, there are plenty of puzzles that cannot be solved using only the techniques you mention. ...

Thanks, everyone. Whew! I'm going to have to brush up on my chains as a technique for solving tough puzzles like this one.

There are a few basics remaining, none of which do any good that I can see.

R7c3<>1 due to locked candidates
R4c2<>8 due to 8 being solved in that row
R3c6<>4 due to locked cand ...

I tried the techniques that I know so far, but I still have WAY too many candidates in this messy puzzle. After "basics," I am at this position:

*-----*-----*-----*-----*-----*-----*-- ...