Sudoku Royal

Four difficulty levels sit under one roof here, from an easy grid that barely pushes back to a genuinely tough one that demands real note-taking. The rules stay pure sudoku: fill the 9x9 grid so every row, column, and 3x3 box holds the digits 1 through 9 with none repeated. Nothing about the presentation reinvents the format, but having a proper easy-to-hard ladder in one place is useful if you're trying to build up from beginner puzzles rather than getting thrown into the deep end.