Sudoku

Sudoku doesn't need selling. It's the same grid it always was, and the appeal is that a well-made puzzle can always be solved by reasoning rather than by trying things.

Sudoku Classic – Daily Brain Puzzle gives you a new one every day, which is the way most people prefer to play it. Sudoku is the straightforward version with no extras attached. Sudoku Village wraps progression around the puzzles so there's a reason to keep going, and Sudoku Blocks takes the grid somewhere different by turning it into a block-placement game. They'll all wait indefinitely while you stare at a row, and that patience is most of why the format has lasted.

There are 5 free games under this tag, all playable in the browser with nothing to install, and they'll all wait indefinitely while you stare at a row.

The wider thinking shelf is Brain games, and Mind Games collects everything that rewards patience over speed.