3D printer modeler

local WindowWidth, WindowHeight = term.getSize()
local shapes = {}

local function main()
    while (true) do
        term.setBackgroundColor(colors.black)
        term.setTextColor(colors.black)
        term.clear()

        paintutils.drawFilledBox(1,1, 16,16, colors.white)

        for x=1,16 do
            term.setCursorPos(x,1)
            local sx = tostring(x)
            if (#sx > 1) then
                term.write(string.sub(sx, 2,2))
            else
                term.write(sx)
            end
        end

        for y=1,16 do
            term.setCursorPos(1,y)
            term.write(y)
        end

        for i,s in ipairs(shapes) do
            paintutils.drawPixel(s.x, s.y, colors.red)
        end

        sleep(0.1)
    end
end

local function mouseActions(button, x, y, isDrag)
    if (x <= 16 and y <= 16 and button == 1) then
        table.insert(shapes, {x=x, y=y})
    elseif (x <= 16 and y <= 16 and button == 2) then
        for i,s in ipairs(shapes) do
            if (x==s.x and y==s.y) then
                table.remove(shapes, i)
                break
            end
        end
    end
end

local function onClick()
    while (true) do
        local event, button, x, y = os.pullEvent("mouse_click")
        mouseActions(button, x, y, false)
    end
end

local function onDrag()
    while (true) do
        local event, button, x, y = os.pullEvent("mouse_drag")
        mouseActions(button, x, y, true)
    end
end

parallel.waitForAny(main, onClick, onDrag)