as

local bBreak = false
local chars = {}
local renderTimer;
local isImportant = {["1"] = true, ["2"] = true, ["3"] = true, ["4"] = true, ["5"] = true, ["6"] = true, ["7"] = true, ["8"] = true, ["9"] = true, ["0"] = true}

function render()
    term.clear()
    term.setCursorPos(15, 2)
    term.write("PIN #:")
    term.setCursorPos(18, 3)
    term.write("[" .. (chars[1] or "-") .. "]")
    term.setCursorPos(22, 3)
    term.write("[" .. (chars[2] or "-") .. "]")
    term.setCursorPos(26, 3)
    term.write("[" .. (chars[3] or "-") .. "]")
    term.setCursorPos(30, 3)
    term.write("[" .. (chars[4] or "-") .. "]")
end

function main()
    renderTimer = os.startTimer(0) -- Initiate rendering
    while true do
        if bBreak then break end
        local evt, p1, p2 = os.pullEvent()

        if evt == "timer" and p1 == renderTimer then
            renderTimer = os.startTimer(0.1)
            render()
        elseif evt == "char" then
            if isImportant[p1] then
                table.insert(chars, p1)
                -- too lazy to check for overflow
            elseif p1 == "x" then
                bBreak = true
            end
        end
    end
end
main()

term.clear()
term.setCursorPos(1,1)