100 Years Sudoku with 100 year's worth of puzzles!

-Num of puzzles
Everyday, you get a easy puzzle and a hard one.
You can solve not only today's puzzle but also past day's puzzle.
You can go back to 1950/1/1. So,there is many many puzzles.

-Difficulty
There are two kinds of difficulty. Easy or Hard.

-Input buttons
Number buttons.
"∀" button for all inputs.
"?" button for a temporary mark.
"X" button to delete.
"<" and ">" buttons to move.
You can solve puzzles comfortably.

-Accomplishment display
How many puzzles you have solved are displayed by month or years.

-What is Sudoku?
Sudoku is a kind of puzzle.
Fill 9x9 cells with numbers from 1 to 9.
The numbers in a 3x3 cells should be different each other.
The numbers in a row should be different each other.
The numbers in a column should be different each other.