Tic Tac Toe

local monitor = peripheral.find("monitor")
local P1 = {}
local P2 = {}
local P1len, P2len = 0,0

function Draw()
    term.setBackgroundColour(colors.white)
    term.clear()

    -- Player 1
    term.setTextColour(colors.blue)
    local first = true
    P1len = 0
    for i,u in pairs(P1) do
        if (first) then
            term.setTextColour(colors.cyan)
            first = false
        else
            term.setTextColour(colors.blue)
        end

        term.setCursorPos(u[1],u[2])
        write("X")
        P1len = P1len + 1
    end

    -- Player 2
    term.setTextColour(colors.red)
    first = true
    P2len = 0
    for i,u in pairs(P2) do
        if (first) then
            term.setTextColour(colors.pink)
            first = false
        else
            term.setTextColour(colors.red)
        end

        term.setCursorPos(u[1],u[2])
        write("O")
        P2len = P2len + 1
    end

    term.setTextColour(colors.black)
    --R1
    term.setCursorPos(3,1)
    write("|")
    term.setCursorPos(5,1)
    write("|")
    --R2
    term.setCursorPos(2,2)
    write("-")
    term.setCursorPos(3,2)
    write("+")
    term.setCursorPos(4,2)
    write("-")
    term.setCursorPos(5,2)
    write("+")
    term.setCursorPos(6,2)
    write("-")
    --R3
    term.setCursorPos(3,3)
    write("|")
    term.setCursorPos(5,3)
    write("|")
    --R4
    term.setCursorPos(2,4)
    write("-")
    term.setCursorPos(3,4)
    write("+")
    term.setCursorPos(4,4)
    write("-")
    term.setCursorPos(5,4)
    write("+")
    term.setCursorPos(6,4)
    write("-")
    --R5
    term.setCursorPos(3,5)
    write("|")
    term.setCursorPos(5,5)
    write("|")
end

function ValidateMove(x, y)
    if (x == 1 or x >= 7 or y > 5) then
        return false
    end

    if ( (x-1)%2 == 0 or y%2 == 0) then
        return false
    end

    for i,u in pairs(P1) do
        if (x == u[1] and y == u[2]) then
            return false
        end
    end

    for i,u in pairs(P2) do
        if (x == u[1] and y == u[2]) then
            return false
        end
    end

    return true
end

local eventclick = "mouse_click"
if (monitor ~= nil) then
    term.redirect(monitor)
    eventclick = "monitor_touch"
end

while (true) do
    parallel.waitForAny(function()
        local validMove = false
        local event, button, x, y

        Draw()
        while (validMove == false) do
            event, button, x, y = os.pullEvent(eventclick)
            if (ValidateMove(x,y)) then
                validMove = true
            end
        end

        if (P1len >= 3) then
            table.remove(P1, 1)
        end
        table.insert(P1, {x,y})

        Draw()
        validMove = false
        while (validMove == false) do
            event, button, x, y = os.pullEvent(eventclick)
            if (ValidateMove(x,y)) then
                validMove = true
            end
        end

        if (P2len >= 3) then
            table.remove(P2, 1)
        end
        table.insert(P2, {x,y})
    end,
    function()
        os.pullEvent("redstone")
        P1 = {}
        P2 = {}
    end)
end