ScreenGui drawing system!

local player = game.Players.LocalPlayer

local frame = script.Parent

local dragging = false

-- turn on dragging when the mouse is pressed or the screen is touched
frame.InputBegan:Connect(function(input)
    if input.UserInputType == Enum.UserInputType.MouseButton1 or input.UserInputType == Enum.UserInputType.Touch then
        dragging = true
    end
end)

-- turn off dragging when its released
frame.InputEnded:Connect(function(input)
    if input.UserInputType == Enum.UserInputType.MouseButton1 or input.UserInputType == Enum.UserInputType.Touch then
        dragging = false
    end
end)

-- helper function to draw one point at the given x,y position
    local function DrawAt(x, y)
        -- need the parent's position so we can subtract it from the child's
        local topLeft = frame.AbsolutePosition

        local point = Instance.new("Frame")
        point.BackgroundColor3 = Color3.fromRGB(0,0,0)
        point.Size = UDim2.fromOffset(5, 5)
        point.Position = UDim2.fromOffset(x - topLeft.X - 5, y - topLeft.Y - 5)
        point.Parent = frame

    end

    -- fired when the mouse or finger moves
    frame.InputChanged:Connect(function(input)
        if dragging and input.UserInputType == Enum.UserInputType.MouseMovement or input.UserInputType == Enum.UserInputType.Touch then
            DrawAt(input.Position.X, input.Position.Y)
        end
    end)