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Discord Luau

Minesweeper

This guide builds a /minesweeper command that generates a Minesweeper board directly in Discord. Every cell is hidden behind a spoiler tag (||..||) - clicking one reveals the emoji beneath. Bombs are :bomb:, safe cells show the count of adjacent bombs as a number emoji.

How it works

Section titled “How it works”

The board is a plain text message. Each cell is formatted as ||:emoji:||, which Discord renders as a clickable spoiler. Clicking a cell reveals it - just like uncovering a square in Minesweeper.

||:one:||||:bomb:||||:one:||
||:one:||||:two:||||:one:||
||:zero:||||:one:||||:zero:||

Because Discord handles each spoiler independently, there is no cascading reveal - every cell must be clicked individually. The board is entirely self-contained in a single message.

Generating the board

Section titled “Generating the board”
local ROWS  <const> = 9
local COLUMNS  <const> = 9
local MINES <const> = 10


local NUMBER_EMOJIS <const> = table.freeze({
    [0] = ":zero:",
    [1] = ":one:",
    [2] = ":two:",
    [3] = ":three:",
    [4] = ":four:",
    [5] = ":five:",
    [6] = ":six:",
    [7] = ":seven:",
    [8] = ":eight:",
})


local function generateBoard(totalRows: number, totalColumns: number, totalMines: number): string
    -- Initialise the mine grid with all cells safe
    local mineGrid: { { boolean } } = {}
    for row = 1, totalRows do
        mineGrid[row] = {}
        for column = 1, totalColumns do
            mineGrid[row][column] = false
        end
    end


    -- Place mines at random positions using rejection sampling
    local placedMines = 0
    while placedMines < totalMines do
        local targetRow = math.random(1, totalRows)
        local targetColumn = math.random(1, totalColumns)
        if not mineGrid[targetRow][targetColumn] then
            mineGrid[targetRow][targetColumn] = true
            placedMines += 1
        end
    end


    -- Count how many of the 8 neighbouring cells contain a mine
    local function countAdjacentMines(row: number, column: number): number
        local adjacentMines = 0
        for rowOffset = -1, 1 do
            for columnOffset = -1, 1 do
                if rowOffset ~= 0 or columnOffset ~= 0 then
                    local neighborRow = row + rowOffset
                    local neighborColumn = column + columnOffset
                    local withinBounds = neighborRow >= 1 and neighborRow <= totalRows
                        and neighborColumn >= 1 and neighborColumn <= totalColumns
                    if withinBounds and mineGrid[neighborRow][neighborColumn] then
                        adjacentMines += 1
                    end
                end
            end
        end
        return adjacentMines
    end


    -- Render each cell as a spoiler-wrapped emoji
    local boardLines: { string } = {}
    for row = 1, totalRows do
        local rowCells: { string } = {}
        for column = 1, totalColumns do
            if mineGrid[row][column] then
                rowCells[column] = "||:bomb:||"
            else
                local adjacentCount = countAdjacentMines(row, column)
                rowCells[column] = `||{NUMBER_EMOJIS[adjacentCount]}||`
            end
        end
        boardLines[row] = table.concat(rowCells)
    end


    return table.concat(boardLines, "\n")
end

The function returns a single string - one row per line, cells joined without spaces so the grid looks compact in Discord.

Registering the command and handling it

Section titled “Registering the command and handling it”
local discord  = require("@self/../luau_packages/discord")
local classes  = require("@self/../luau_packages/classes")
local builders = require("@self/../luau_packages/builders")
local env      = require("@self/../.env")


local minesweeperCommand = builders.interaction.interaction.new()
    :setName("minesweeper")
    :setDescription("Generates a Minesweeper board. Click the spoilers to reveal cells!")
    :setType("ChatInput")
    :addIntegrationType("GuildInstall")
    :addContext("Guild")
    :build()


local bot = discord.bot.new({
    token = env.DISCORD_BOT_TOKEN,
    intents = builders.intents.new({ "Guilds" }):build(),
    reconnect = true,
})


bot.onAllShardsReady:listenOnce(function()
    local result = bot.application:createSlashCommandAsync(minesweeperCommand):await()


    if result:isErr() then
        warn("Failed to register /minesweeper:", result:unwrapErr())
        return
    end


    print(`Bot '{bot.user.username}' is online!`)
end)


bot.onCommandInteraction:listen(function(interaction: classes.TypesCommand)
    if interaction.data.name ~= "minesweeper" then
        return
    end


    local boardContent = generateBoard(ROWS, COLUMNS, MINES)


    interaction:messageAsync(
        builders.message.message.new()
            :setContent(boardContent)
            :build()
    ):await()
end)


bot:connectAsync():await()

Board size and message length

Section titled “Board size and message length”

Discord messages have a 2000-character limit. The worst-case cell length is ||:eight:|| (11 characters), so a 9×9 board uses at most 11 × 81 + 8 = 899 characters - well within the limit.

SizeMinesMax characters
9×910~899
10×1015~1,109
12×1225~1,595

Avoid going above roughly 13×13 or you risk hitting the limit.

Full script 
local discord  = require("@self/../luau_packages/discord")
local classes  = require("@self/../luau_packages/classes")
local builders = require("@self/../luau_packages/builders")
local env      = require("@self/../.env")


local ROWS  <const> = 9
local COLUMNS  <const> = 9
local MINES <const> = 10


local NUMBER_EMOJIS <const> = table.freeze({
    [0] = ":zero:",
    [1] = ":one:",
    [2] = ":two:",
    [3] = ":three:",
    [4] = ":four:",
    [5] = ":five:",
    [6] = ":six:",
    [7] = ":seven:",
    [8] = ":eight:",
})


local function generateBoard(totalRows: number, totalColumns: number, totalMines: number): string
    local mineGrid: { { boolean } } = {}
    for row = 1, totalRows do
        mineGrid[row] = {}
        for column = 1, totalColumns do
            mineGrid[row][column] = false
        end
    end


    local placedMines = 0
    while placedMines < totalMines do
        local targetRow = math.random(1, totalRows)
        local targetColumn = math.random(1, totalColumns)
        if not mineGrid[targetRow][targetColumn] then
            mineGrid[targetRow][targetColumn] = true
            placedMines += 1
        end
    end


    local function countAdjacentMines(row: number, column: number): number
        local adjacentMines = 0
        for rowOffset = -1, 1 do
            for columnOffset = -1, 1 do
                if rowOffset ~= 0 or columnOffset ~= 0 then
                    local neighborRow = row + rowOffset
                    local neighborColumn = column + columnOffset
                    local withinBounds = neighborRow >= 1 and neighborRow <= totalRows
                        and neighborColumn >= 1 and neighborColumn <= totalColumns
                    if withinBounds and mineGrid[neighborRow][neighborColumn] then
                        adjacentMines += 1
                    end
                end
            end
        end
        return adjacentMines
    end


    local boardLines: { string } = {}
    for row = 1, totalRows do
        local rowCells: { string } = {}
        for column = 1, totalColumns do
            if mineGrid[row][column] then
                rowCells[column] = "||:bomb:||"
            else
                local adjacentCount = countAdjacentMines(row, column)
                rowCells[column] = `||{NUMBER_EMOJIS[adjacentCount]}||`
            end
        end
        boardLines[row] = table.concat(rowCells)
    end


    return table.concat(boardLines, "\n")
end


local minesweeperCommand = builders.interaction.interaction.new()
    :setName("minesweeper")
    :setDescription("Generates a Minesweeper board. Click the spoilers to reveal cells!")
    :setType("ChatInput")
    :addIntegrationType("GuildInstall")
    :addContext("Guild")
    :build()


local bot = discord.bot.new({
    token = env.DISCORD_BOT_TOKEN,
    intents = builders.intents.new({ "Guilds" }):build(),
    reconnect = true,
})


bot.onAllShardsReady:listenOnce(function()
    local result = bot.application:createSlashCommandAsync(minesweeperCommand):await()


    if result:isErr() then
        warn("Failed to register /minesweeper:", result:unwrapErr())
        return
    end


    print(`Bot '{bot.user.username}' is online!`)
end)


bot.onCommandInteraction:listen(function(interaction: classes.TypesCommand)
    if interaction.data.name ~= "minesweeper" then
        return
    end


    local boardContent = generateBoard(ROWS, COLUMNS, MINES)


    interaction:messageAsync(
        builders.message.message.new()
            :setContent(boardContent)
            :build()
    ):await()
end)


bot:connectAsync():await()

References

Section titled “References”
  • Bot - the discord.bot class, gateway connection and event emitters
  • Interaction builder - builders.interaction.interaction, constructs slash command definitions
  • Message builder - builders.message.message, constructs response payloads
  • Intents builder - builders.intents, constructs the gateway intent bitfield
  • Futures - the FutureLike async primitive returned by async calls