Help with camera manipulation?

I'm trying to get the camera to follow the mouse.

https://vimeo.com/266586757 -- I'm very close but its kind of weird because the speed changes and doesn't really stay on track with the mouse.

https://vimeo.com/266512080 -- part invis

I'm assuming that it has something to do with my delta (change in pos)

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local Player = game.Players.LocalPlayer



local move_vector = Vector3.new(0,0,0)
local speed = .001
local scroll_speed = 6
local mouse = game.Players.LocalPlayer:GetMouse()
local lastx, lasty = mouse.X, mouse.Y


local userInput = game:GetService("UserInputService")
local runService = game:GetService("RunService")

local focus = Instance.new("Part")
focus.Anchored = true
focus.CanCollide = false
focus.Transparency = 1
focus.Size = Vector3.new(0.1,0.1,0.1)
focus.Position = Vector3.new(0,2,0)
focus.Parent = Player
focus.Name = "Focus"

local function Panned(input, processed)
    if not processed and input.UserInputType == Enum.UserInputType.MouseMovement then
        local delta = input.Delta
      if userInput.MouseBehavior ~= Enum.MouseBehavior.LockCenter then
         -- If locked, then calculate delta:
         delta = Vector2.new(mouse.X - lastx, mouse.Y - lasty)
      end
      lastx, lasty = mouse.X, mouse.Y
        panDeltaMouse = delta
    end
end

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userInput.InputChanged:Connect(function(input,processed)
if input.UserInputType == Enum.UserInputType.MouseMovement and MouseButton then
Panned(input,processed)
move_vector = move_vector+Vector3.new(panDeltaMouse.X,0,panDeltaMouse.Y)
print("Moving to: ",move_vector)
end
end)
------------------------------------------------

game:GetService("RunService").RenderStepped:Connect(function()
    focus.Position = focus.Position + (move_vector)*speed
end)