How would I make the player's arms and head follow the mouse? [R15]

well, here is a script, place it in starterGUI in a LocalScript.

wait()



local Ang = CFrame.Angles   
local aSin = math.asin
local aTan = math.atan



local Cam = game.Workspace.CurrentCamera

local Plr = game.Players.LocalPlayer
local Mouse = Plr:GetMouse()
local Body = Plr.Character or Plr.CharacterAdded:wait()
local Head = Body:WaitForChild("Head")
local Hum = Body:WaitForChild("Humanoid")
local Core = Body:WaitForChild("HumanoidRootPart")
local IsR6 = (Hum.RigType.Value==0) 
local Trso = (IsR6 and Body:WaitForChild("Torso")) or Body:WaitForChild("UpperTorso")
local Neck = (IsR6 and Trso:WaitForChild("Neck")) or Head:WaitForChild("Neck")  
local Waist = (not IsR6 and Trso:WaitForChild("Waist")) 



local MseGuide = false


local TurnCharacterToMouse = false

local HeadHorFactor = 1
local HeadVertFactor = 0.6
local BodyHorFactor = 0.5
local BodyVertFactor = 0.4


local UpdateSpeed = 0.5

local NeckOrgnC0 = Neck.C0  
local WaistOrgnC0 = (not IsR6 and Waist.C0) 



Neck.MaxVelocity = 1/3

if TurnCharacterToMouse == true then
    MseGuide = true
    HeadHorFactor = 0
    BodyHorFactor = 0
end

game:GetService("RunService").RenderStepped:Connect(function()
    local CamCF = Cam.CoordinateFrame
    if ((IsR6 and Body["Torso"]) or Body["UpperTorso"])~=nil and Body["Head"]~=nil then 
        local TrsoLV = Trso.CFrame.lookVector
        local HdPos = Head.CFrame.p
        if IsR6 and Neck or Neck and Waist then 
            if Cam.CameraSubject:IsDescendantOf(Body) or Cam.CameraSubject:IsDescendantOf(Plr) then
                local Dist = nil;
                local Diff = nil;
                if not MseGuide then    
                    Dist = (Head.CFrame.p-CamCF.p).magnitude
                    Diff = Head.CFrame.Y-CamCF.Y
                    if not IsR6 then    
                        Neck.C0 = Neck.C0:lerp(NeckOrgnC0*Ang((aSin(Diff/Dist)*HeadVertFactor), -(((HdPos-CamCF.p).Unit):Cross(TrsoLV)).Y*HeadHorFactor, 0), UpdateSpeed/2)
                        Waist.C0 = Waist.C0:lerp(WaistOrgnC0*Ang((aSin(Diff/Dist)*BodyVertFactor), -(((HdPos-CamCF.p).Unit):Cross(TrsoLV)).Y*BodyHorFactor, 0), UpdateSpeed/2)
                    else    
                        Neck.C0 = Neck.C0:lerp(NeckOrgnC0*Ang(-(aSin(Diff/Dist)*HeadVertFactor), 0, -(((HdPos-CamCF.p).Unit):Cross(TrsoLV)).Y*HeadHorFactor),UpdateSpeed/2)
                    end
                else
                    local Point = Mouse.Hit.p
                    Dist = (Head.CFrame.p-Point).magnitude
                    Diff = Head.CFrame.Y-Point.Y
                    if not IsR6 then
                        Neck.C0 = Neck.C0:lerp(NeckOrgnC0*Ang(-(aTan(Diff/Dist)*HeadVertFactor), (((HdPos-Point).Unit):Cross(TrsoLV)).Y*HeadHorFactor, 0), UpdateSpeed/2)
                        Waist.C0 = Waist.C0:lerp(WaistOrgnC0*Ang(-(aTan(Diff/Dist)*BodyVertFactor), (((HdPos-Point).Unit):Cross(TrsoLV)).Y*BodyHorFactor, 0), UpdateSpeed/2)
                    else
                        Neck.C0 = Neck.C0:lerp(NeckOrgnC0*Ang((aTan(Diff/Dist)*HeadVertFactor), 0, (((HdPos-Point).Unit):Cross(TrsoLV)).Y*HeadHorFactor), UpdateSpeed/2)
                    end
                end
            end
        end
    end
    if TurnCharacterToMouse == true then
        Hum.AutoRotate = false
        Core.CFrame = Core.CFrame:lerp(CFrame.new(Core.Position, Vector3.new(Mouse.Hit.p.x, Core.Position.Y, Mouse.Hit.p.z)), UpdateSpeed / 2)
    else
        Hum.AutoRotate = true
    end
end)