Target Shooting Game

local targetPos = {}
local score = 0
local hits = 0
local misses = 0
local maxX, maxY = term.getSize()
local startTime = os.clock()
local difficulty = 1
local chain = 0

local function getDifficulty()

    local function printButton(x,y,text)
        term.setBackgroundColor(colors.blue)
        term.setCursorPos(x,y)
        for i=1, string.len(text)+2 do
            write(" ")
        end
        term.setCursorPos(x,y+1)
        term.write(" ")
        term.write(text)
        term.write(" ")
        term.setCursorPos(x,y+2)
        for i=1, string.len(text)+2 do
            write(" ")
        end
        term.setBackgroundColor(colors.black)
        return
    end

    local function Button_pointCollideCheck(x,y,button)
        for i,v in ipairs(button) do
            local currentX, currentY = unpack(v)
            if x == currentX and y == currentY then
                return i
            end
        end
        return false
    end
    term.setBackgroundColor(colors.black)
    term.clear()
    local buttons = {}
    term.setCursorPos(1,1)
    print("T A R G E T  S H O O T I N G")
    print("")
    print("DIFFICULTY: ")
    print("")
    printButton(2, 5, "HARD")
    printButton(2, 9, "MEDIUM")
    printButton(2, 13, "EASY")
    while true do
        local event, button, x, y = os.pullEvent()
        if event == "mouse_click" then
            if (x >= 2 and x <=6) and (y >= 5 and y <= 9) then -- the lower, the harder
                difficulty = 0.75
                return
            elseif (x >= 2 and x <= 8) and (y >= 9 and y <= 13) then
                difficulty = 1
                return
            else
                difficulty = 1.25
                return
            end
        end
    end
end

getDifficulty()

local function pointCollideCheck(x,y)
    for i,v in ipairs(targetPos) do
        local currentX, currentY = unpack(v)
        if x == currentX and y == currentY then
            return i
        end
    end
    return false
end

local function setTarget(x,y)
    targetPos = {
        {x,y}, {x+1,y}, {x+2,y},
        {x,y+1}, {x+1,y+1}, {x+2,y+1},
        {x,y+2}, {x+1,y+2}, {x+2,y+2},
    }
    for i,v in ipairs(targetPos) do
        local x,y = unpack(v)
        if x > maxX then
            return false
        elseif y > maxY-1 then
            return false
        end
    end
    return true
end


local function drawScreen()
    term.setBackgroundColor(colors.black)
    term.clear()
    term.setCursorPos(1,1)
    for i,v in ipairs(targetPos) do
        term.setCursorPos(unpack(v))
        if i == 5 then
            term.setBackgroundColor(colors.red)
        else
            term.setBackgroundColor(colors.white)
        end
        term.write(" ")
    end
    term.setBackgroundColor(colors.black)
    term.setCursorPos(1, maxY)
    term.write("Score: "..score.." Hits: "..hits.." Misses: "..misses.." Accuracy: "..math.floor((hits/(hits+misses))*100).."%")
    term.setCursorPos(1,1)
    local multi = (chain/10)*1.5
    term.write("Chain: "..chain.." Multiplier: "..multi.." Playtime: "..(math.floor((os.clock()-startTime)*10)/10).."s")
end

local function game_logicThread()
    math.randomseed(os.clock())
    local firstX = math.random(1, maxX-3)
    local firstY = math.random(2, maxY-3)
    setTarget(firstX, firstY)
    local timer = os.startTimer(difficulty)
    while true do
        local event, param1, param2, param3 = os.pullEvent()
        if event == "mouse_click" then
            term.setCursorPos(param2, param3)
            local x = param2
            local y = param3
            local collide = pointCollideCheck(x,y)
            if collide then
                if collide == 5 then
                    term.setBackgroundColor(colors.red)
                else
                    term.setBackgroundColor(colors.white)
                end
                term.setTextColor(colors.orange)
                term.write("*")
                term.setTextColor(colors.white)
                term.setBackgroundColor(colors.black)
                chain = chain+1
                hits = hits+1
                local multi = (chain/10)*1.5
                if collide == 5 then
                    if multi >= 1 then
                        score = score+(multi*2)
                    else
                        score = score+2
                    end
                else
                    if multi >= 1 then
                        score = score+multi
                    else
                        score = score+1
                    end
                end
                targetPosTable = {}
                math.randomseed(os.clock())
                local newX = math.random(1, maxX-3)
                local newY = math.random(2, maxY-3)
                setTarget(newX, newY)
                timer = os.startTimer(difficulty)
            else
                term.setBackgroundColor(colors.black)
                term.setTextColor(colors.orange)
                term.write("*")
                term.setTextColor(colors.white)
                score = score-1
                misses = misses+1
                chain = 0
            end
        elseif event == "timer" and param1 == timer then
            score = score-1
            chain = 0
            targetPosTable = {}
            math.randomseed(os.clock())
            local newX = math.random(1, maxX-3)
            local newY = math.random(2, maxY-3)
            setTarget(newX, newY)
            timer = os.startTimer(difficulty)
        end
    end
end

local function game_drawThread()
    while true do
        drawScreen()
        os.sleep(0)
    end
end

term.clear()
term.setCursorPos(1,1)
parallel.waitForAll(game_logicThread, game_drawThread)