Overview and quickstart

This page should provide sufficient information to help you to decide if you want to try the program, and, if so, enough about the interface to enable you to get started. A more succinct summary of how to use the program is available in the Frequently asked questions (FAQ). However, should you want to do a complete read through, the easiest way is to use the "Next" links at the head and foot of the navigation menu on the left of each page. Some may be more interested in the descriptions of the solving techniques than the program. At present (April, 2007) there are 22 pages.

The first screen dump illustrates the interface and some of the program's features. It shows a partially completed grid. Above the grid is a row of menus and a toolbar. Below the grid are numbers describing the current state of play. The menus and toolbar give access to a range of options which can be employed to aid solving the puzzle. This includes automatic flagging of inconsistent or incorrect answers, quick filtering out of the possibilities for cells, facilities for colouring selected cells and specific symbols to help detect patterns, and hints from the application of several algorithms including Naked pairs, Naked triples, Naked quads, Hidden singles, Hidden pairs, Hidden triples, Locked candidates 1, Locked candidates 2 and Xwing Swordfish Jellyfish

The large numbers in the grid are the solutions for the cells, and the small numbers in each cell are the remaining candidates for each cell. These small numbers not only show the remaining possibilities, but are actually buttons which can be used to turn the symbols on and off. Hence the program can be used as a kind of notepad of the possibilities still remaining for each cell (obviously, for unsolved clues, all 9 are "on" when the puzzle is started).

The state shown is one in which the user has asked for a hint and the program has shaded green 13 candidates which together constitute a Naked quad pattern for the box in the bottom right corner. The program has also shaded in red two other candidates in the same box. This means that these two candidates can be removed. Their removal is achieved simply by clicking on them with the left mouse button. Alternatively, to set the solution for a cell the user clicks on the corresponding button with the right mouse button. This will set the large symbol in the centre of the cell and switch off all the small ones. In this example, the symbol "2" can be set for the cell with the red shaded candidates because the hint has shown that all the other symbols are impossible. So the user right clicks on the "2". (Alternatively, if the user clicks in turn on the two red buttons in this cell, the program would automatically set the cell value to 2.) If the user discovers that the solution for a cell has been set incorrectly, all nine symbols can be reactivated by clicking on the bottom right hand button in the cell. Note that the hint can also be executed by left clicking on the red button in the Toolbar. i.e. clicking on the Toolbar with the left mouse button will automatically remove all candidates shaded red by the hint. Conversely, the hint can be turned off by right clicking on the red button in the Toolbar. (The hint found is explained in the Naked quad section: the symbols 3,5,8 and 9 are the only four symbols in four cells in a single box so they must, between them, be the solutions to those cells: these symbols can hence be removed from all other cells in the box).

Hints can be requested for specific "algorithms" by clicking on their symbol in the Toolbar. Alternatively, if the user clicks on the "?" option in the Toolbar the program will try all of its algorithms. Then, depending on the current search strategy it will either report the hint which removes the most candidates or the simplest hint. In the example shown the program has also highlighted in red the button "N4" in the "Toolbar" at the top, so the user knows that the Naked quads algorithm is providing the hint.

The hint mechanism can be configured to shade in the candiates that can be removed, to shade only the candidates that form the pattern (ie the green shaded ones in Figure 1), or to shade only the cells involved in the pattern.

The program has a set of built-in puzzles but puzzles can also be read from files read from files or entered via a simple text text editor window. Puzzles can be saved to files.

The puzzles are given a numerical difficulty rating depending on the algorithms required in their solution.

The raised areas in the centre of each cell which contain the symbols for the solved clues are also buttons. In this case, menu buttons, and they give access to options which can be applied to the individual cell, including showing the correct solution and colouring the cell to aid the search for patterns. A related option in the File menu allows the user to request that all symbols of a particular type, say all 2's, are set to a given colour, again to aid pattern recognition.

The program remembers every step made while a puzzle is being worked on. The user can go back one step at a time using the < button on the Toolbar, or can go back to the last consistent state with a single click on the << button

The "s" and "S" buttons in the Toolbar execute a simple filter, in which the symbols set in completed cells are turned off in all the unsolved cell's if they are in the same row, column or box. "S" does one step at a time and is subject to the hint mechanism, but "s" instantly performs as many such operations as are possible for the current state of the grid. Although purists may deprecate its use, "s" can save a lot of tedious mouse clicks and give the user more time to work on the interesting parts of problems.

The five numbers beneath the grid give the Puzzle Number, the number of steps taken by the User, the number of states recorded (History), the remaining Information content, of the puzzle (actually the total number of candidates left, here 176), and the time taken in seconds.