(UnityEngine) Simple Physics-Based Character Controller

PlayerController.cs

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerController : MonoBehaviour
{
    [SerializeField] private Transform camera;
    
    [SerializeField] private float velocity;
    [SerializeField] private float acceleration;
    [SerializeField] private float skinWidth;
    [SerializeField] private float jumpForce;
    [SerializeField] private float groundDrag;
    [SerializeField] private float airDrag;
    
    [SerializeField] private LayerMask groundLayerMask;

    private Rigidbody _rigidbody;
    [SerializeField] private bool grounded;

    private void Awake()
    {
        _rigidbody = GetComponent<Rigidbody>();
    }

    void FixedUpdate()
    {
        Movement();
        LimitVelocity();
    }

    private void Update()
    {
        CheckGround();
    }

    private void LimitVelocity()
    {
        Vector3 currentVelocity = Vector3.ProjectOnPlane(_rigidbody.velocity, Vector3.up);

        if (currentVelocity.magnitude > velocity)
        {
            Vector3 limitVel = currentVelocity.normalized * velocity;
            limitVel.y = _rigidbody.velocity.y;
            
            _rigidbody.velocity = limitVel;
        }
    }

    void Movement()
    {
        Vector3 input = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical")) * velocity;
        Vector3 movement = camera.TransformDirection(input);
        movement = Vector3.ProjectOnPlane(movement, Vector3.up).normalized * input.magnitude;
        
        _rigidbody.AddForce(movement * acceleration * velocity, ForceMode.Force);
    }

    void CheckGround()
    {
        grounded = GroundCheck();

        _rigidbody.drag = grounded ? groundDrag : airDrag;
            
        if (grounded && Input.GetKeyDown(KeyCode.Space))
        {
            Jump();
        }
    }

    void Jump()
    {
        _rigidbody.AddForce(Vector3.up * jumpForce);
    }

    bool GroundCheck()
    {
        RaycastHit rhit;
        Physics.Raycast(transform.position, -Vector3.up, out rhit, 1f + skinWidth, groundLayerMask);
        return rhit.collider;
    }
}