Assets/Scripts/PlayerController.cs

using UnityEngine;

namespace UnityAgent
{
    /// <summary>
    /// Third-person character controller with WASD movement, jump and a
    /// rigidbody-based physics response. Designed to be paired with the
    /// ThirdPersonCamera component.
    /// </summary>
    [RequireComponent(typeof(Rigidbody))]
    [RequireComponent(typeof(CapsuleCollider))]
    public class PlayerController : MonoBehaviour
    {
        [Header("Movement")]
        public float moveSpeed = 6f;
        public float sprintMultiplier = 1.6f;
        public float rotationSmooth = 12f;
        public float jumpForce = 7.5f;

        [Header("Ground Check")]
        public float groundCheckDistance = 0.2f;
        public LayerMask groundMask = ~0;

        [Header("Camera")]
        public Transform cameraTransform;

        private Rigidbody _rb;
        private CapsuleCollider _col;
        private Vector2 _moveInput;
        private bool _jumpRequested;
        private bool _isGrounded;
        private float _targetRotation;

        private void Awake()
        {
            _rb = GetComponent<Rigidbody>();
            _col = GetComponent<CapsuleCollider>();
            _rb.freezeRotation = true;
            _rb.interpolation = RigidbodyInterpolation.Interpolate;
            if (cameraTransform == null && Camera.main != null)
                cameraTransform = Camera.main.transform;
        }

        private void Update()
        {
            _moveInput.x = Input.GetAxisRaw("Horizontal");
            _moveInput.y = Input.GetAxisRaw("Vertical");
            _moveInput = Vector2.ClampMagnitude(_moveInput, 1f);

            if (Input.GetButtonDown("Jump") && _isGrounded)
                _jumpRequested = true;
        }

        private void FixedUpdate()
        {
            GroundCheck();
            Move();
            if (_jumpRequested)
            {
                _rb.AddForce(Vector3.up * jumpForce, ForceMode.VelocityChange);
                _jumpRequested = false;
            }
        }

        private void GroundCheck()
        {
            Vector3 origin = transform.position + Vector3.up * (_col.height * 0.5f - _col.radius);
            _isGrounded = Physics.SphereCast(
                origin, _col.radius * 0.9f, Vector3.down,
                out _, groundCheckDistance, groundMask, QueryTriggerInteraction.Ignore);
        }

        private void Move()
        {
            float speed = moveSpeed;
            if (Input.GetKey(KeyCode.LeftShift)) speed *= sprintMultiplier;

            if (_moveInput.sqrMagnitude < 0.01f)
            {
                // Apply horizontal damping so the character stops cleanly.
                Vector3 v = _rb.velocity;
                v.x *= 0.85f;
                v.z *= 0.85f;
                _rb.velocity = v;
                return;
            }

            Vector3 camForward = cameraTransform ? cameraTransform.forward : transform.forward;
            Vector3 camRight = cameraTransform ? cameraTransform.right : transform.right;
            camForward.y = 0f; camForward.Normalize();
            camRight.y = 0f; camRight.Normalize();

            Vector3 desired = (camForward * _moveInput.y + camRight * _moveInput.x) * speed;
            Vector3 velocity = _rb.velocity;
            velocity.x = desired.x;
            velocity.z = desired.z;
            _rb.velocity = velocity;

            if (desired.sqrMagnitude > 0.01f)
            {
                _targetRotation = Mathf.Atan2(desired.x, desired.z) * Mathf.Rad2Deg;
                float smoothed = Mathf.LerpAngle(
                    transform.rotation.eulerAngles.y, _targetRotation,
                    Time.fixedDeltaTime * rotationSmooth);
                _rb.MoveRotation(Quaternion.Euler(0f, smoothed, 0f));
            }
        }
    }
}