GridLab is an iPad app for designing Sudoku puzzles to solve by hand, not on screen. You set the constraints, generate the grid, then export to PDF, PNG, SVG, or EPUB for paper, physical media, or e-ink. 5 combinable variants: Classic, X-Sudoku, Anti-King, Anti-Knight, Hyper. Every puzzle shows its logical depth, clue density, and whether it requires guessing to solve. No hints, no gamification, no ads, no subscription. A voluntary tip is the only ask. Free to download. iPad only.