Yamsweeper is a game to clear the field filled with bombs (mines).  On the left
top corner of the main window, the number of mines left is displayed.  You can
mark hidden mines underneath the panels, then the number is decreased.  The
number can be minus, but that means you have over-marked.  On the right top
corner, the time passed is displayed.  The time counts up to 999 seconds.  On
center top, there's the symbol of yamsweeper.  You can start a new game by
clicking the symbol.  A panel is opened with the left mouse button.  If unopened
panels are around the panel, and if they don't have mines underneath and around
them, panels are also opened.  This can happen like a chain reaction.  Be
careful; the game is over when you open a mine.  If the panel opened has mines
around, you will see a number varies from 1 to 8, which means the number of
mines.  For example, `1' tells you one of the panels around has a mine. `2' says
that two mines are hidden next to.  You can mark suspicious panels by the right
button, which toggles the state of the panel between "Bomb" or "?" (in which it
cannot be opened) and Normal.  The middle button is assigned a special
functionality.  You can use the middle button to open the unmarked panels
around, under certain conditions:
-  the panel you clicked is opened
-  the panel is not null, a number is displayed
-  the number of marked panels is equal to the number displayed on the
   clicked panel.
Click the middle button on a opened panel.