\subsection{Sudoku}
\label{ref:Sudoku}
\screenshot{plugins/images/ss-sudoku}{Sudoku}{fig:sudoku}
Sudoku in Rockbox can act as both a plugin and a viewer.
When starting Sudoku from the \setting{Browse Plugins} menu, a 
random game will be generated automatically, and an estimate of its difficulty
(very easy, easy, medium, hard or fiendish) will be displayed on the screen.
New games can be generated from the \setting{Generate} menu option.
When ``playing'' an existing Sudoku game file from Rockbox' file browser
the plugin is invoked as viewer. The selected Sudoku will get loaded and you
can start solving it. The sudoku games need to be stored as text
files with the extension \fname{.ss} as single file per game.

You can create and save your own grids under the \setting{New} menu option.
Enter the menu (as described in the key table below) when you have finished and
enter the full path to save to including the \fname{.ss} extension 
(e.g. \fname{/sudoku/new.ss}).

\subsubsection{The scratchpad}
When you play Sudoku on paper most people like to mark numbers in cells that 
are possible candidates for the cells.
This can be done with the scratchpad, shown as separate column.
Change the number under the cursor to the number you want to put on the
scratchpad and press the scratchpad button, the number will then be added.
If the number was already on the scratchpad it will get removed again.
The column is stored separately for every cell on the board. The stored values
can be displayed inline as small dots by enabling the \setting{Show Markings}
settings.
\note{The scratchpad is \emph{not} saved when saving the game.}

\begin{btnmap}
    \opt{IRIVER_H100_PAD,IRIVER_H300_PAD,IAUDIO_X5_PAD%
        ,SANSA_E200_PAD,SANSA_FUZE_PAD,SANSA_C200_PAD,SANSA_CLIP_PAD,GIGABEAT_PAD%
        ,GIGABEAT_S_PAD,MROBE100_PAD,PBELL_VIBE500_PAD,SANSA_FUZEPLUS_PAD%
        ,SAMSUNG_YH92X_PAD,SAMSUNG_YH820_PAD,RG_NANO_PAD}
        {\ButtonUp{} / \ButtonDown{} / \ButtonLeft{} / \ButtonRight}
    \opt{IPOD_4G_PAD,IPOD_3G_PAD}{\ButtonScrollFwd{} / \ButtonScrollBack}
    \opt{IRIVER_H10_PAD}{\ButtonScrollUp{} / \ButtonScrollDown{} / \ButtonLeft{} / \ButtonRight}
    \opt{COWON_D2_PAD}{\TouchTopMiddle{} / \TouchBottomMiddle{} / \TouchMidLeft{} / \TouchMidRight}
    \opt{MPIO_HD200_PAD}{\ButtonRew / \ButtonFF / \ButtonVolDown / \ButtonVolUp}
    \opt{MPIO_HD300_PAD}{\ButtonScrollUp / \ButtonScrollDown / \ButtonRew / \ButtonFF}
    \opt{XDUOO_X3_PAD}{\ButtonPrev / \ButtonNext / \ButtonHome / \ButtonOption}
  \opt{HAVEREMOTEKEYMAP}{& }
    & Move the cursor\\
    %
    \opt{IPOD_4G_PAD,IPOD_3G_PAD}{\ButtonSelect & Change cursor move direction\\}
    %
    \opt{IRIVER_H100_PAD,IRIVER_H300_PAD}{\ButtonSelect{} / \ButtonOn}
    \opt{IPOD_4G_PAD,IPOD_3G_PAD}{\ButtonLeft{} / \ButtonRight}
    \opt{IAUDIO_X5_PAD,GIGABEAT_PAD,GIGABEAT_S_PAD,MROBE100_PAD%
         ,SANSA_FUZEPLUS_PAD}{\ButtonSelect}
    \opt{SANSA_FUZEPLUS_PAD}{; \ButtonBottomRight / \ButtonBottomLeft}
    \opt{IRIVER_H10_PAD}{\ButtonRew}
    \opt{SANSA_E200_PAD,SANSA_FUZE_PAD}{\ButtonScrollBack{} / \ButtonScrollFwd}
    \opt{SANSA_C200_PAD,SANSA_CLIP_PAD}{\ButtonSelect{} / \ButtonVolUp{} / \ButtonVolDown}
    \opt{COWON_D2_PAD}{\TouchCenter}
    \opt{PBELL_VIBE500_PAD}{\ButtonOK}
    \opt{MPIO_HD200_PAD}{\ButtonFunc}
    \opt{MPIO_HD300_PAD}{\ButtonEnter}
    \opt{SAMSUNG_YH92X_PAD,SAMSUNG_YH820_PAD}{\ButtonFF{} / \ButtonRew}
    \opt{XDUOO_X3_PAD}{\ButtonPlay ; \ButtonVolUp / \ButtonVolDown}
    \opt{RG_NANO_PAD}{\ButtonA}
  \opt{HAVEREMOTEKEYMAP}{& }
    & Change number under the cursor\\
    %
    \opt{IRIVER_H100_PAD,IRIVER_H300_PAD}{Long \ButtonOn}
    \opt{IPOD_4G_PAD,IPOD_3G_PAD}{Long \ButtonLeft{} / \ButtonRight}
    \opt{IAUDIO_X5_PAD,GIGABEAT_PAD,GIGABEAT_S_PAD,MROBE100_PAD%
         ,SANSA_FUZEPLUS_PAD}{Long \ButtonSelect}
    \opt{SANSA_FUZEPLUS_PAD}{; Long \ButtonBottomRight{} / Long \ButtonBottomLeft}
    \opt{IRIVER_H10_PAD}{Long \ButtonRew}
    \opt{SANSA_E200_PAD,SANSA_FUZE_PAD}{Long \ButtonScrollBack{} / \ButtonScrollFwd}
    \opt{SANSA_C200_PAD,SANSA_CLIP_PAD}{Long \ButtonSelect{} / \ButtonVolUp{} / \ButtonVolDown}
    \opt{COWON_D2_PAD}{Long \TouchCenter}
    \opt{PBELL_VIBE500_PAD}{Long \ButtonOK}
    \opt{MPIO_HD200_PAD}{Long \ButtonFunc}
    \opt{MPIO_HD300_PAD}{Long \ButtonEnter}
    \opt{SAMSUNG_YH92X_PAD,SAMSUNG_YH820_PAD}{Long \ButtonFF{} / Long \ButtonRew}
    \opt{XDUOO_X3_PAD}{Long \ButtonPlay ; Long \ButtonVolUp / Long \ButtonVolDown}
    \opt{RG_NANO_PAD}{Long \ButtonA}
  \opt{HAVEREMOTEKEYMAP}{& }
    & Constantly changing the number under the cursor\\
    %
    \opt{IRIVER_H100_PAD,IRIVER_H300_PAD}{\ButtonMode}
    \opt{IPOD_4G_PAD,IPOD_3G_PAD,GIGABEAT_PAD,GIGABEAT_S_PAD,MROBE100_PAD%
      ,COWON_D2_PAD,PBELL_VIBE500_PAD,MPIO_HD300_PAD}{\ButtonMenu}
    \opt{IAUDIO_X5_PAD,IRIVER_H10_PAD}{\ButtonPlay}
    \opt{SANSA_E200_PAD}{\ButtonSelect}
    \opt{SANSA_FUZE_PAD}{\ButtonHome}
    \opt{SANSA_C200_PAD,SANSA_CLIP_PAD,XDUOO_X3_PAD}{\ButtonPower}
    \opt{MPIO_HD200_PAD,SAMSUNG_YH820_PAD}{\ButtonRec}
    \opt{SANSA_FUZEPLUS_PAD}{\ButtonBack}
    \opt{SAMSUNG_YH92X_PAD}{Long \ButtonPlay}
    \opt{RG_NANO_PAD}{\ButtonB}
  \opt{HAVEREMOTEKEYMAP}{& }
    & Open Menu\\
    %
    \opt{IRIVER_H100_PAD,IRIVER_H300_PAD,IAUDIO_X5_PAD,SANSA_E200_PAD,SANSA_C200_PAD}{\ButtonRec}
    \opt{SANSA_CLIP_PAD}{\ButtonHome}
    \opt{SANSA_FUZE_PAD}{\ButtonSelect}
    \opt{IPOD_4G_PAD,IPOD_3G_PAD,GIGABEAT_S_PAD,PBELL_VIBE500_PAD,MPIO_HD200_PAD%
        ,MPIO_HD300_PAD,SANSA_FUZEPLUS_PAD,SAMSUNG_YH92X_PAD,SAMSUNG_YH820_PAD}{\ButtonPlay}
    \opt{IRIVER_H10_PAD}{\ButtonFF}
    \opt{GIGABEAT_PAD}{\ButtonA}
    \opt{MROBE100_PAD}{\ButtonDisplay}
    \opt{COWON_D2_PAD}{Long \TouchBottomLeft}
    \opt{XDUOO_X3_PAD}{\ButtonHome + \ButtonPower}
    \opt{RG_NANO_PAD}{\ButtonX}
  \opt{HAVEREMOTEKEYMAP}{& }
    & Add/Remove number to scratchpad\\
    %
    \opt{IRIVER_H100_PAD,IRIVER_H300_PAD}{\ButtonOff}
    \opt{IAUDIO_X5_PAD,IRIVER_H10_PAD,SANSA_E200_PAD,GIGABEAT_PAD,GIGABEAT_S_PAD%
      ,MROBE100_PAD}{\ButtonPower}
    \opt{SANSA_FUZE_PAD}{Long \ButtonHome}
    \opt{IPOD_4G_PAD,IPOD_3G_PAD,SAMSUNG_YH92X_PAD,SAMSUNG_YH820_PAD}{Menu $\rightarrow$ Quit}
    \opt{SANSA_C200_PAD,SANSA_CLIP_PAD,COWON_D2_PAD,XDUOO_X3_PAD}{Long \ButtonPower}
    \opt{PBELL_VIBE500_PAD}{\ButtonRec}
    \opt{MPIO_HD200_PAD}{\ButtonRec+\ButtonPlay}
    \opt{MPIO_HD300_PAD}{Long \ButtonMenu}
    \opt{RG_NANO_PAD}{\ButtonStart}
  \opt{HAVEREMOTEKEYMAP}{& }
    & Quit\\
    %
\end{btnmap}

Some places where can you can find \fname{.ss} files:
\begin{itemize}
\item Simple Sudoku (Advanced Puzzle Packs 1 and 2 located near the bottom of that page):
\url{http://www.angusj.com/sudoku/}
\item Kjell's Sudoku generator/solver:
\url{http://kjell.haxx.se/sudoku/}
\end{itemize}
