Bands
Each live game uses the same bands: Beginner, Easy, Medium, Hard, Expert, Extreme.
A band is the kind of reasoning the puzzle asks for. It is not how empty the grid looks. A Beginner board can have many empty cells and still be gentle. A harder band asks you to hold more of the board in mind, and to use tighter deductions.
Start on Beginner. Move up when the current band feels like a walk, not when you want a fight. The names are ordinary. They are not a score.
The four live games — Sudoku, Star Battle, Binary Puzzle, and Killer Sudoku — all speak this way. Pick a band for the sit you want, then play.