*
*          * * * * * * * * * * * * * * * * * 
*         *                                 *
*         *   MINE FIELD Construction Kit   *
*         *                                 *
*          * * * * * * * * * * * * * * * * *
*
* Unless otherwise specified, all coordinates are expressed
* in units of "tiles" (1-40 horizontally, 1-25 vertically).
*
*-------------------------------------------------------------------------
*
Task drawfield ( Int a , Int b , Int c , Int d ) 
*
* Draws a field of gray tiles inside a gray frame.
*
* Enter with:
*
*      (a,b) - the coordinates of the upper-left tile in the frame.
*      (c,d) - the coordinates of the lower-right tile in the frame.
*                      
Task plantmine ( Int x , Int y ) 
*
* Puts a mine at location (x,y) if no mine is already there.
*
Task removemine ( Int x , Int y ) 
*
* Removes a mine from location (x,y) if a mine is there.
*
Task plantmines ( Int n ) 
*
* Randomly fills the field with mines.
* (Each tile has 1/n chance of receiving a mine.)
*
Task shownulls 
*
* Uncovers all tiles whose mine proximity count is zero.
*
Task autoproc ( Int mode , Int err , Int x , Int y ) 
*
* Uncovers and/or marks all tiles whose identities are "obvious".
*
* Enter with:
*        mode=0, (do nothing)
*        mode=1, mark all obvious tiles
*        mode=2, uncover all obvious tiles
*        mode=3, mark and uncover all obvious tiles
*
* Return with:
*        err=0, no mines were uncovered
*        err<0, then (x,y) is location of uncovered mine
*
Task togglemarker ( Int x , Int y ) 
*
* Toggles on or off the mine marker on tile (x,y)
*
Task reveal ( Int x , Int y , Int z ) 
*
* Uncovers the tile at location (x,y) and displays
* the mine proximity count for that location.  If
* no mine is uncovered, returns z=0.  If a mine is
* revealed, it is displayed on a red square, and the
* value -1 is returned in z.
*
Task testfordone ( Int z ) 
*
* Looks to see if all tiles have been either uncovered
* or marked as mines.  If so, returns z=1.  Otherwise,
* returns z=0.
*
Task showmines 
*
* Reveals all unmarked mines in the field.
* If a tile was incorrectly marked, a red
* "X" is displayed on that tile.
*
Task pixeltotile ( Int x , Int y ) 
*
* Converts the numerical values of (x,y) from pixel
* coordinates [640x480] into tile coordinates [40x25].
*
Task tiletopixel ( Int x , Int y ) 
*
* Converts the numerical values of (x,y) from tile
* coordinates [40x25] into pixel coordinates [640x480]
* centered on the tile.
*
Task status ( Int x , Int y , Int visible , Int marked , Int mine ) 
*
* Returns the current state of the tile located at (x,y):
*
*   visible - 0: tile has not yet been revealed
*             4: tile has been revealed
*    marked - 0: tile is not currently marked as covering a mine
*             2: tile is currently marked as covering a mine
*      mine - 0: tile is not actually covering a mine
*             1: tile is actually covering a mine
*
Task neighbors ( Int x , Int y , Int visible , Int marked , Int mines ) 
*
* Returns the proximity counts [0-8] for the tile located at (x,y):
*
*   visible: number of neighboring tiles that have been revealed
*    marked: number of neighboring tiles that have been marked
*     mines: number of neighboring tiles that are covering a mine
*
*
Task waitmouse ( Int x , Int y , Int z ) 
*
* Waits until a mouse button is pushed and released.
* It then returns the current location (x,y) of the
* mouse (in tile coordinates) along with the button
* value (z).
*
* [If a graphics button on the screen has been pressed,
* returns in z the negative id value of the button.  If
* the 'Esc' key is pressed, terminates the program.]
*
Task drawbutton ( Int id , Text label , Int color ) 
*
* Draws a gray button on the screen at the current cursor position.
*
* Enter with:
*        id - the button's ID number (1-32)
*     label - the label to be drawn on the button
*     color - the color of the surrounding rectangle
*
*
Task victory
*
* Plays a bugle call.
*
*-------------------------------------------------------------------------
*
* [The following tasks are intended for internal use only, but are made
* available for those advanced users who may want to access them.]
*
Task drawmine ( Int x , Int y ) 
Task drawoops ( Int x , Int y ) 
Task drawredx ( Int x , Int y ) 
Task drawtextile ( Text t , Int color , Int x , Int y ) 
Task drawtile ( Int x , Int y )