I'm an absolute beginner and was stuck at the first puzzle of Sven's Sudoku Pad. I reached the following board state, where I noted for every cell which values were possible:
After a while I simply tried to brute force a solution. I set the value of the cell
5, which quickly resulted in a contradiction: I could not place a
7 in the bottom middle 3x3 block. After that I was able to solve the puzzle quite easily.
My question is which technique (instead of pure brute force) I should have applied here. I tried reading up on Y wings and similar techniques, but spotting and applying them are quite hard indeed.