Sudoku: Dark is a one-rule puzzle game that can be either satisfyingly simple or deceptively difficult. Puzzles have four difficulty levels: easy , medium , hard, and expert! Choose any level you like!

How to play sudoku?
- Sudoku puzzle consists of a grid of 9 blocks.
- Each block contains 3 rows and 3 columns grid.
- Some grids are pre-filled with numbers, which cannot be changed.
- The objective is to fill all the grids with 1 to 9 numbers, and each column, each row, and each of block contains only one of each digit.

FEATRURES：
- Free to play
- No time limited
- Turn on the pen mode to take notes like paper. Each time you fill in a cell, the notes update automatically!
- Four different difficulties
- Unique solution for each puzzle
- Highlight cells which are in same row, column and block.