How to make source engine-like movement?

Hey, I was just wondering how to make movement like source engine or nextbots game, I’ve researching for a while but i didnt find any

the Q3PlayerController.cs script mimics the source engine/quake movement really well. In fact, the Accelerate and ApplyFriction functions are almost line for line the same ones used in the original source/quake engines, aside from the fact that they were written in different languages.

there is also

ive been using these to help me recreate the movement in my own game.