Platinum Sudoku offers 20 million Sudoku puzzles (in five levels of difficulty), over 300 Kakuro puzzles and a number of mini-games. The game starts with a tutorial mode and the twenty million puzzles will only be available to you after completing 100 puzzles in Easy, Medium or Hard mode. Solving all puzzles in Hard mode unlocks the Pro mode, solving the Pro puzzles unlocks the Sudoku X mode. New background graphics, fonts, grid styles and music are also unlockable.
The object of Sudoku is to fill a square grid measuring 9x9 spaces, further divided into nine 3x3 squares with the numbers 1 to 9. Each horizontal row and each vertical column can only contain each number once, and this also applies to each of the square grids. Each grid already contains a few numbers, how many depends on the level of difficulty. The game layout can be switched around for left-handed players by choosing an option from the menu.
Filling the grid is done by either drawing the desired character directly onto the grid on the Touch Screen, by pointing to that number on a small grid or by using the D-pad. Several numbers can be entered in one cell in Draft mode. When the player has deduced which number is the only one possible, the choice is made definitive. It is possible to ask for hints, but these cost "coins" that have to be earned by solving puzzles. Hint A gives some possible numbers for the current cell, Hint B provides the correct number for the current cell, and Hint C scans the whole board and marks cells as right or wrong. It is also possible to choose several assisting features from the game menu, for instance highlighting the current row or column, highlighting the "easiest to solve" cells or automatically filling the grid with all possibilities for each cell.
Kakuro puzzles are like crosswords except the grids are filled with numbers. The grid consists of black and white cells. The white cells must be filled with numbers, the black cells contain the clues. Each entry can only contain a number (between 0 and 9) once and the sum of the numbers must match the clue. For example if the clue is "11" and the entry is three cells wide, the solution could be "1, 6, 4" or "2, 5, 4" but not "2, 7, 2".
The mini-games included in Platinum Sudoku are Subtract (drop numbers unto others to subtract them until you reach zero), Pair Match (draw lines between pairs of numbers), Shuffle (slider puzzle), Choice Block (find the missing number), High Sum (choose the block with the highest sum) and Mine Detector (mine sweeper). If a challenge is met, the game is unlocked in the menu and you can try to improve your high score.
Two players can play co-op to solve a grid together or compete to see who is the fastest in solving a grid. Finally there is a Custom Grid mode which allows you to design your own puzzles.