Here are some key features of this game:

- unlimited number of puzzles

- autosave, save, load function

- pencil mark mode

Use mouse or cursor keys to move cursor. Move cursor on a blank cell to enter the digit.

Press Del or Backspace or button with eraser to erase a digit.

Click on the pencil button to turn on pencil marks mode. Then click on a cell to place a pencil mark in the cell, or remove the pencil mark if there is one already.

Click on the pen button to turn off pencil mark mode.

To save or load a games go to File menu. Last game saved always.

Here are some key features of this game:

- user interface is simple, intuitive and have a nice simple look

- unlimited number of puzzles

- five level of difficulty

- autosave, save, load function

- pencil mark mode