Sudoku is a logic puzzle with simple rules and challenging solutions.

The rules of sudoku are simple.
You have to enter a numerical digit from 1 through 9 in each cell of a 9x9 grid made up of 3x3 regions, starting with various digits given in some cells. Each row, column, and region must contain only one instance of each numeral.

Zooming
Pinch with two fingers to zoom in/out. If you use a mouse you can use the scroll button.

Moving
Tap and drag to move the puzzle. If you use a mouse you can click and drag with the middle (scroll) button.

Entering numbers
You can tap/click individual cells to make them active. After that tap/click one of the number buttons to enter the number.

Game modes and sizes

• You can change the game you play from the "hamburger" menu at the top-right corner.
• You can change the mode / size of the current game from the top menu (click on the down arrow at the top/middle)
• There are 2 modes which you can play
  • Random - this mode loads a random puzzle from the chosen size
  • Quest - this mode requires you to login. You can then solve a sequence of puzzles with increasing difficulty.

Other helpful tips

• You can get rid of the address bar and gain extra playing space by dragging the header or the footer quickly upwards so you scroll the page a bit down. It's tricky and you need practice. iOS8+ users - this will be just temporary until you click something in the bottom bar - sad story I know.
• If you are left handed or just playing with your left hand there is a spacial option in the settings just for you.
• Try the different helpers in the settings - some will make the puzzle too easy for you, others may automate some trivial tasks.