The classic 9×9 route
Easy, Medium, and Hard all use the same 1–9, row–column–3×3-box contract. The distinction is information density: fewer easy placements, more sustained elimination, and a larger role for clean notes as the ladder rises.
Sudoku Cosmos ladder
Difficulty should feel like a route,
Difficulty should feel like a route,
not a cliff.
The Android edition is built as a continuous progression: four classic 9×9 tiers, then a separate 16×16 format. Names tell players where they are; the rules remain honest about what changes.
0102030405
- 01Easy Orbit9×9
200 generous-to-tighter 9×9 boards for visible pattern confidence.
- 02Medium Drift9×9
200 9×9 boards with one fewer clue at entry and a denser information field.
- 03Hard Surge9×9
200 9×9 boards that continue beyond Medium through measured pressure bands.
- 04Killer Apex9×9
200 final 9×9 boards. Standard classic rules; no cages or sum clues.
- 05Beyond Infinity16×16
200 16×16 boards with 4×4 regions and a different scale of observation.
Killer is our last 9×9 level—not cage-sum Killer Sudoku.
Killer Apex is Sudoku Cosmos’s final classic 9×9 difficulty label. It uses standard rules only. It does not use cages, arithmetic sums, or a separate Killer Sudoku variant.
Read the Killer level note →Read the Evil Sudoku guide →Beyond changes the board to 16×16.
Beyond Infinity is not merely a tougher 9×9 label. It has 256 cells and 4×4 regions, so it receives its own page, rules context, and interface treatment.
Visit Beyond →