Use the cursor keys to quickly move through the cells. Backspace/Delete clears a cell. Using the on-screen keyboard (or keyboard letters A to Z) you can enter ’candidates’. Selecting a letter a second time changes the candidate to your final letter.
The aim of the puzzle is to enter one of 9 letters in each cell. The letters you can use are shown in the box on the left. In every row, column and box those letters may only occur once. Some cells already contain letters (called givens), you need to fill the empty cells. Your end goal is to find the word on the diagonal.