Buttons within each cell are used to set and unset its symbols and colourings and to perform operations on that individual cell.
The little buttons
When a puzzle is loaded the user is presented with a grid showing the starting clues, and, for each of the unsolved cells, their nine possibilities. A typical starting grid is shown in Figure 1.
The symbols 1-9 and the letter "R" shown in small font in the unsolved cells are the labels of little buttons. When a button showing a number is clicked using the left mouse button, the number is removed. See below (the "R" button) about how to restore the symbol.
These little buttons are also used to set the solution for a cell. This is achieved by clicking with the right mouse button. When this is done all the candidate buttons in the cell lose their symbols and are inactivated and the "R" button loses its label. At the same time the selected symbol appears on a white background in large font in the centre of the cell. However, even though the "R" button has lost its label, it is still active and can be used to reset the candidates.
When looking for patterns of symbols it can be helpful to colour individual buttons. One way this can be achieved is by use of the middle mouse button: click on a little button with the middle mouse button and it will be shaded with a the current default colour; click on it again and it will will revert to the background colour. See the section Colouring symbols for more information about this.
By employing the little buttons in the simple ways just described the program can be used as a notebook for solving Kakuro puzzles.
The large coloured rectangles in the centres of cells are also buttons. Clicking on these areas pops up a menu of options that can be applied on the corresponding cell. See Figure 2.
The first menu item reveals the answer for the cell. Undo will clear it. The second menu item will change the background colour of the cell to help identify patterns in the grid.
The numbers giving the row and column sums are also buttons. If the user clicks on them a pop-up will appear showing all the combinations for the current row or column sum. As cells are solved the combinations are altered to accord with the new sum. See Figure 3.