I have recently moved up to more difficult puzzles and, at the same time, tried to learn more advanced techniques as well. But on this one I'm currently stuck. I've tried more advanced stuff like skyscraping and kiting, but I must admit defeat at this point. This puzzle is still solvable (according to the software, so I've been getting it right thus far) but the next step eludes me completely.
I would be very grateful if someone could give me an idea on what to look for or which technique I can use to advance (the technique itself I can read up on on my own, just need to know which one). This could be an excellent opportunity for me to gather one more tool to my... ...well... ...collection of tools. Many thanks to anyone participating in my sudoku skills advancement!