The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Luigi Fonti:
NumberGrid is a board game, somehow similar to Sudoku.You have a 6x6 grid. Each cell contains a number, 0 to 9; some of them are shown, some other are hidden.On the right of each row, and at the bottom of each column, the sum is shown of all the elements of that row, or column.Matching these indications, you have to guess the values assigned to hidden cells.To unveil a cell, just tap on it: a numerical keyboard will appear, and you can enter the number you guessed. If your guess was correct, the cell will assume a yellow background, and the hidden digit will be shown.If your guess was wrong, you still have two more attempts (three in total) to strike the right value; otherwise the hidden digit will be shown with a gray background, and your move will be marked as a fault.When all the cells will be unveiled, an alert message will notify your success, or the total number of faults.Before starting a new game, you can choose the level: Easy or Difficult: this will affect the starting number of exposed cells.