Lua Minesweeper

math.randomseed(os.time())
local realBoard = {}
local myBoard = {}

-- settings:
width = 9       -- board width
height = 9      -- board height
mines = 10      -- mine count
deterministic = false   -- avoid 50/50 guess cases
openFirstMove = false   -- ensure first move lands on a tile with 0 surrounding mines

-- beginner : 9x9/10
-- intermediate : 16x16/40
-- expert   : 30x16/99

local function shuffle(table)
    local buffer
    for i = #table, 1, -1 do
        local r = math.random(1,i)
        buffer = table[i]
        table[i] = table[r]
        table[r] = buffer
    end
end

local function isValid(x, y)
    return x>0 and x<=width and y>0 and y<=height
end

local function getNeighbors(i)
    local neighbors = {}
    local x = (i-1)%width + 1
    local y = math.floor((i-1)/width)+1

    for ix = x-1, x+1 do
        for iy = y-1, y+1 do
            if isValid(ix, iy) then
                table.insert(neighbors, ix+(iy-1)*width)
            end
        end
    end

    return neighbors
end

local function labelTiles()
    for i, bomb in ipairs(realBoard) do
        if bomb then
            for _, n in ipairs(getNeighbors(i)) do
                if not realBoard[n] then
                    myBoard[n] = myBoard[n]+1
                else
                    myBoard[n] = "■"
                end
            end
        end
    end
end

local function printBoard()
    for y = 1, height do
        local row = ""
        for x = 1, width do
            local i = x+(y-1)*width
            local v = myBoard[i]
            if v ~= 0 then
                row = row..myBoard[i].." "
            else
                row = row.."  "
            end
        end
        print(row)
    end
end

local function clamp(n, min, max)
    if n < min then return min end
    if n > max then return max end
    return n
end

local function setup()
    realBoard = {}
    myBoard = {}

    mines = clamp(mines, 1, width*height-1)
    for i = 1, width*height do
        myBoard[i] = 0
        realBoard[i] = false
        if i <= mines then
            realBoard[i] = true
        end
    end

    shuffle(realBoard)
    labelTiles()
end

setup()
printBoard()