Nikoli has the BEST sudoku puzzles
The app has a clean interface, and quality of sudoku puzzles is still unmatched at all skill levels. They are always thoughtfully designed, and you can sense a “flow” in the logic when solving (randomly generated puzzles often lack this experience).
I am a long-time fan and supporter of Nikoli puzzles from when they used to appear in GAMES magazine back in the early 2000’s and their online puzzle platform (please bring this back!!).
I miss the multi-player environment of their online platform where you could see how others solved the same puzzle, and compare times. It helped me improve my skills immensely. I hope they can develop their apps further to bring some of that magic back. 🤞.