proc spel {{size 10}} {
    global spel
    catch {destroy .frame}

    catch {
      toplevel $w
      wm title $w {Bert Bos Puzzle}
      wm iconname $w {Bert Bos Puzzle}
    }
    frame .frame
    pack .frame -fill both -expand 1 -fill both
    set col $size
    while {$col > 0} {
	frame .frame.t$col
	pack .frame.t$col -expand 1 -fill both
	set row 1
	while {$row <= $size} {
	    set vrij($col,$row) blue
	    button .frame.t$col.$row -width 1 -height 1 -relief raised \
		-borderwidth 1 -padx 0 -pady 0 -bg $vrij($col,$row) \
		-command "press $row $col $size"
	    pack .frame.t$col.$row -side left -fill both -expand 1
	    set row [expr $row + 1]
	}
	set col [expr $col - 1]
    }
    frame .frame.tok
    set new 3
    while {$new < 14} {
	button .frame.tok.$new -command "spel $new" -text $new
	pack .frame.tok.$new -side left -fill both -expand 1
	set new [expr $new + 1]
    }
    frame .frame.stok
    while {$new < 24} {
	button .frame.stok.$new -command "spel $new" -text $new
	pack .frame.stok.$new -side left -fill both -expand 1
	set new [expr $new + 1]
    }
    button .frame.quit -command "destroy ." -text Quit
    pack  .frame.tok .frame.stok  .frame.quit  -fill both -expand 1
}

proc press {col row size} {
    swap $col $row $size
    swap [expr $col+1] [expr $row] $size
    swap [expr $col-1] [expr $row] $size
    swap [expr $col] [expr $row+1] $size
    swap [expr $col] [expr $row-1] $size
}

proc swap {col row size} {
    if { $col > 0 && $row > 0 && $col <= $size && $row <= $size } {
	set color [lindex [.frame.t$row.$col configure -bg] 4] 
	if {$color == "blue"} {
	    .frame.t$row.$col configure -bg red 
	} { .frame.t$row.$col configure -bg blue }
    }
}

spel 6