Fill in the grid with numbers from 1 to the grid size, so that every number appears exactly once in each row and column, and so that all the < signs represent true inequalities.
Use the cursor keys to quickly move through the cells. Backspace/Delete clears a cell. Using the on-screen numpad (or keyboard numbers 1 to 9) you can enter 'candidates'. Selecting a number a second time changes the candidate to your final number.
