joey, I feel your frustration. I have only done one expert without an educated guess. Most only take 2 options but there are a few that take about a dozen goes. I've tried to figure out the advanced techniques people go on about but to no avail.
Joey, keep working it. As incredible as it may seem the brain has the ability to rewire itself - called neuroplasticity - which it does every day, pruning what we don't use and adding to what we do. Proven with identical twin studies. It does get easier. ng,ng
It had two unique rectangles. Cute. 14.
What is considered a guess? If you know a square can only hold 2 values, does picking one and placing a green then seeing where that trails takes you a guess? Or do you have to follow the trail in your mind before adding a value to that square in order to be no guess?
Phil and joey, when looking to build Sudoku skills, there are some basic techniques that are worth learning thoroughly because they combine to do a lot of the work involved in solving most puzzles.
The basic techniques I find most useful are: manual greens; crosshatching; and looking to complete rows, columns or boxes that have only one, two or three cells open.
It is also possible to use crosshatching in a more advanced way so as to eliminate some less obvious impossibilities from manual greens. I call this technique virtual crosshatching.
You may already be using some of these techniques, but even so it is easy to miss their full potential unless you learn to push them and combine them. Many people only discover their full potential by practicing with these techniques many, many times. Fortunately there are a huge number of practice puzzles available in the IronSudoku archives.
You may be surprised to see greens on the list as many players think of greens as a way to cheat. Personally I find them to be a valuable learning tool which helps me to see and understand patterns that are otherwise difficult to identify and study. I am not talking about using some lines of code to display all the greens in the puzzle at once, I mean figuring out for yourself the greens in individual cells one by one, especially for cells you think will help you. And I don't mean you should necessarily use greens a lot, a little or only when you're really stuck - it's entirely up to you. Stop using greens when you can do puzzles without them because by that time you will have learned what you needed to learn.
tuco, some people say using one or more greens is cheating, and others don't. Some people say successive testing and elimination of possibilities is cheating, and others don't.
Personally I believe that testing a "what happens if?" is just as valid as trying to identify how various cells are dependent on one other and then eliminating impossibilities.
On the other hand, blind guessing without keeping track of what possibility you are testing seems pointless to me because you won't learn from what you are doing.
Ultimately it's a choice between following practices advocated by people who think they know what you should be doing or not doing, and making up your own mind based on wanting to develop your own understanding of the patterns and relationships you can discover through many attempts to solve puzzles by a variety of methods.