How can I make the player's arm move in a 2D Axis?

Hello there!

I’ve recently found a script I’m currently using for a Terraria “Remake”. Anywho, it works perfectly fine, although since my game is going to be 2D, I’m trying to make the arms move in a 2D Axis as shown here:
ezgif.com-cut (2)

This is what it looks like in-game however:
robloxapp-20240507-1706256-ezgif.com-crop

I know I can fix this by actually using MousePos.X and MousePos.Y but I don’t know how I can change it. Here’s the script:

--//Player
local Player = game:GetService("Players").LocalPlayer
local Character = Player.Character or Player.CharacterAdded:Wait()
--//Arms
local RightArm = Character:FindFirstChild("Right Arm")
local LeftArm = Character:FindFirstChild("Left Arm")
local Mouse = Player:GetMouse()

local RightShoulder = Character.Torso:FindFirstChild("Right Shoulder")
local LeftShoulder = Character.Torso:FindFirstChild("Left Shoulder")

--//
local RunService = game:GetService("RunService")
local function Point_C0_To_Mouse(Motor6D, WorldCFrame)
	local Part1_CFrame = Motor6D.Part1.CFrame
	local Stored_C1 = Motor6D.C1
	local Stored_C0 = Motor6D.C0
	local RelativeTo_Part1 = Stored_C0 * Stored_C1:Inverse() * Part1_CFrame:Inverse() * WorldCFrame * Stored_C1
	RelativeTo_Part1 -= RelativeTo_Part1.Position

	local Goal_C0 = RelativeTo_Part1 + Stored_C0.Position
	return Goal_C0
end


RunService.Stepped:Connect(function()
	local Mouse_Pos = Mouse.Hit.Position
	RightShoulder.C0 = Point_C0_To_Mouse(RightShoulder, CFrame.lookAt(RightArm.Position, Mouse_Pos)) * CFrame.Angles(0,0, math.deg(-90))
end)

bump 1 since nobody seems to notice