Sudoku Puzzles

Maen!
I have finally published another blog page, Y wing styles.
If you care to visit, the link is found at the top of the right column.

9:48, but one mistake....still working on time.

There's that bird again.

I have NEVER seen a hummingbird sit still for so long!! Two days now!!!?

That is a brilliant photo. I tried for hours to capture a photo of one and all I got was a blur about a meter away when my flash accidentally triggered.

Hi Steve, the key to this puzzle is the almost unique rectangle?

Good afternoon to all! I agree it's a nice picture Ian, but it's about the 10th time we've seen it. Why GATH?

I'm getting tired of the repeats too. Does that mean more could be submitted? I have some nice pictures from this spring when some of my friends came out and we did the touristy thing here. He probably just has a lot backed up though.

Still very rare and far between that I can get a puzzle without guessing - today is no exception, I used 3 or 4. Oh well. It's still solved eventually.

Oh, the Hummer! I am looking forward to Springtime. I guess I had better start buying sugar.

Hi kateblu!
I am finding this puzzle completely non-trivial.
I have not used an almost unique rectangle in any of the solutions that I came up with. If you found such a step, please, if you can, detail it for us. My current proofs are very long, and very deep, and very ugly.

I've just submitted 6 more pictures to the Tough and 3 to the Hard - mostly from yesterday's trip to Jenolan Caves.

Not easy today!

I must have done something wrong becuase i found it easy normally have to guess but this one just fell into place

CG,tenth time??think you missed a zero next to it...

for the love of god PLEASE stop posting this picture! ENOUGH!!!

I was bored so I reformatted some of my pictures and submitted them. Only a few, but hopefully they'll be in some day - I think they're all quite neat looking!

Looking forward to seeing your photo's Karen I think Gath will have to delete some of the older ones.

A proof for tough!!!!! sudoku of 01 07 2007:

1) Start at 23 filled - the given puzzle. Unique Possibilities to 26 filled. (UP 26).
2a) Hidden pair 13 at d5e4 forbids d5=9,e4=259
2b) Locked 9's at de6 forbids ag6=9
2c)g2=4 == g2=5 -- g79=5 == h9=5 -- h9=7 == h123=7 -- i2=7 == i2=4 More...

Sorry - very late post of proof.
If anyone studies this proof, the long step is not very interesting, just long.

But, step3c is very interesting - it can also be represented as a depth 5 Sue de Coq, albeit I prefer the depth 4 Hidden Sue de Coq used.

Also, step 3g is a complex fc More...

Hi STEVE from Ohio,

can you explain for me how to forbids h9=439 and i13=7 at your step 2c? thanks

Hi ttt!
Refer perhaps to the blog, Y wing styles, to see an example of a wrap around forbidding chain, ableit in the blog it is only depth 3.

In 2c, the chain is depth 4, but since the endpoints of the chain are mutually weak, and they are proven strong, all the weak links in the chain More...

Quite difficult today

Dec. 21, 2007. I agree, Nick.

SE=8.4