function tile_reveal(x,y)
    if y > 0
    and y <= #board.board
    and x > 0
    and x <= #board.board[1] then
        if board.overlay[y][x] == 11 then
            if board.board[y][x] != 9 then
                for d=1,#dirs do
                    if y+dirs[d][2] > 0
                    and y+dirs[d][2] <= #board.board
                    and x+dirs[d][1] > 0
                    and x+dirs[d][1] <= #board.board[1]
                    and board.overlay[y+dirs[d][2]][x+dirs[d][1]] == 11 then
                        board:change_overlay(x+dirs[d][1],y+dirs[d][2],0)
                    end
                end
            end
            board:change_overlay(x,y,0)
        end
    end
end