The Arm will automatically Follow the Mouse This is made using an algorithm called inverse kinematics used for procedural joints. There are many methods to implement it. I have used an easier method involving trigonometry and... circles?
I made this a long long time ago after seeing a project on Youtube. Unfortunately I have forgotten where I learnt all the mathematics for this from. Vector Math Engine by @jebiminecraft, it's very well-structured, 10/10 recommended