The app's levels

In brief

The app offers four levels: Easy, Medium, Hard and Inhuman. The higher the level, the fewer digits the grid gives at the start. Each level draws from 100 grids that come with the app, all with a unique solution. You can also enter your own grid with Custom.

The grids of each level

Level	Given digits	Cells to fill	Grids included	Solved with singles alone
Easy	50	31	100	100 out of 100
Medium	40	41	100	100 out of 100
Hard	30	51	100	100 out of 100
Inhuman	20	61	100	79 out of 100

All the grids of a level have exactly the same number of given digits, and each has only one solution: the site's verification tool recounted this with the app's solver, grid by grid. A new game picks a grid at random from those of the chosen level. The last column shows how many can be finished using only the basic techniques; see the techniques.

What each level looks like

5	empty	empty	empty	3	4	empty	6	9
4	2	6	8	empty	9	5	3	7
3	8	empty	6	5	7	empty	2	1
1	empty	5	empty	empty	3	2	empty	empty
8	3	7	empty	9	empty	empty	4	6
6	9	2	4	8	empty	7	5	empty
2	1	empty	empty	7	6	empty	8	empty
empty	5	empty	9	2	empty	6	empty	4
9	6	empty	empty	empty	empty	3	empty	empty

Easy: grid no. 1, 50 given digits.

7	empty	5	empty	2	4	8	6	empty
empty	empty	9	empty	empty	5	2	empty	empty
4	empty	1	empty	9	6	empty	empty	5
empty	5	empty	2	empty	9	empty	empty	6
empty	9	7	empty	empty	empty	5	empty	empty
2	6	empty	empty	5	8	9	empty	1
empty	4	empty	6	empty	empty	1	5	7
empty	1	6	9	empty	7	empty	empty	8
8	7	empty	empty	empty	empty	empty	9	empty

Medium: grid no. 8, 40 given digits.

6	empty	9	8	empty	empty	empty	empty	empty
2	empty	empty	empty	empty	empty	8	1	empty
empty	7	empty	empty	empty	3	4	empty	empty
7	empty	1	3	empty	empty	empty	empty	8
empty	5	4	empty	empty	empty	6	empty	empty
empty	empty	empty	6	1	9	empty	empty	empty
empty	2	empty	empty	7	empty	1	6	3
empty	8	empty	empty	empty	5	empty	empty	empty
3	empty	7	empty	empty	empty	2	empty	5

Hard: grid no. 14, 30 given digits.

empty	2	empty	4	empty	empty	empty	7	empty
empty	8	3	empty	1	empty	empty	empty	empty
empty	empty	empty	empty	empty	empty	empty	empty	empty
7	empty	empty	empty	2	empty	empty	4	empty
empty	empty	empty	6	empty	9	empty	empty	empty
empty	empty	empty	empty	8	empty	empty	empty	empty
5	empty	empty	empty	empty	empty	1	empty	8
6	empty	empty	7	3	2	empty	empty	empty
empty	empty	empty	empty	empty	empty	3	empty	empty

Inhuman: grid no. 22, 20 given digits.

Custom: enter your own grid

Custom opens an empty grid where you copy the digits of a grid found elsewhere, in a newspaper for example. The confirm button only becomes active once 17 digits are placed. The app then looks for the solution with its solver: if there is exactly one, the game starts; if there is none or more than one, the app goes back to the entry screen, without any message. The Examples page shows a grid rejected this way.

Grid creation screen in the Sudoku app on a phone: the entered given digits and their counter, an eraser and a save button to the left of the number pad, below them a cross to cancel and a check mark to confirm. — Entering a personal grid.

Saved games

The Saved games screen keeps the last 20 solved grids: level, time and starting grid. You can delete one, or replay it from the start; a Custom grid cannot be replayed from this screen.