Using hints

The hint mechanism is one of the program's most important features. By using the hint options in their full range of settings, and by refering to the explanations in these web pages, users should be able to greatly improve their puzzle solving skills.

By left clicking on the corresponding button in the Toolbar the user can select a specific algorithm to be applied to search for a hint. Alternatively the "?" button in the Toolbar or the "Give hint" option in the Edit menu can be used. In the latter cases the program will use its current search strategy and find an appropriate hint using any of the currently active algorithms. The resulting hint is then displayed.

The hint display provides two classes of information about the patterns found: it can colour the Toolbar to show which algorithm or class of algorithm found the hint, and it can colour the cells and candidates involved in the hint. Depending on the level of help they want, the users can specify the amount of detail each of these provides.

Showing hint patterns

The hint display is selected using the "Set hint level" option in the File menu. The program uses the terms "causing" for the candidates which create the pattern and "affected" for the candidates which can be removed because of the pattern.

Setting "Highlight cells" puts the program into a mode in which it will identify cells which cause the pattern (yellow) and which can have candidates removed (pink) (see Figure 1). If the cell from which candidates can be removed is the same as the one providing the basis for their removal (as in the case of "Hidden singles"), then the cell will be shaded pink.

Setting "Highlight only causing candidates" requests that only candidates that cause/create the pattern will be shaded (green) (see Figure 2).

Setting "Highlight only affected candidates" requests that only candidates that can be removed will be shaded (red) (see Figure 3).

Setting "Highlight candidates" puts the program into a mode in which it will identify the candidates which can be removed in red and the causing candidates in green (see Figure 4).

To stop anything being shown about the hint's cells or candidates, the option "Highlight nothing" should be selected.

All hint settings remain in place until the user removes all the affected candidates, either by left-clicking on them or left-clicking on the red shaded buttons in the Toolbar; cancels the hint by right-clicking on the red shaded buttons in the Toolbar; requests "undo", or starts a new puzzle.

Note that many algorithms need the Simple filter to be applied exhaustively before they can be effective. Because of this, Simple filter will always be used automatically before a search using any other algorithm. This can be performed explicitly by a single application of "Apply simple filter exhaustively", ("s" in the Toolbar), which operates outside the hint mechanism.

For all of the above options, the program will colour red the button of the algorithm for which the hint was found. For those users who do not want such explicit information, the options described below alter this behavior.

Identifying hint algorithms

When a hint is found the program always colours the "?" button in the Toolbar red and activates it so that it can be used to execute (left click) the hint (i.e. delete the candidates) or to dismiss (right click) the hint. If the user selects "Show only "?"" in "Set hint level" in the File menu, none of the other buttons in the Toolbar will be shaded red when a hint is found i.e. the identity of the algorithm will be hidden. If the option "Show only group" is selected the program will colour red all the Toolbar buttons in the same algorithm group as that of the found hint. Any of the red buttons can be used to execute or dismiss the hint.

Algorithm groups

When the program starts, algorithm groups are set as follows: [H1,H2,H3], [L1,L2], [N2,N3,N4], [XW,SF,JF], i.e. 4 groups. However, if the Show difficulty/Set scores option in the File menu is activated, the user can change the scores for each of the algorithms. Hereafter, any algorithms with the same score will occupy the same group. For example one user sets the following algorithm scores:

1 for N1 "&" H1
2 for L1 "&" L2
3 for N2 "&" N3
6 for H2, H3 "&" N4
9 for XW, SF 
20 for JF

To stop an algorithm from being used in the search for hints, its algorithm score should be set to zero.