Basic FPS Camera

using UnityEngine;

[RequireComponent(typeof(CharacterController))]
public class FPSCamera : MonoBehaviour
{
    [Header("Movement")]
    public float moveSpeed = 5f;
    public float sprintSpeed = 8f;
    public float gravity = -9.81f;

    [Header("Mouse Look")]
    public float mouseSensitivity = 200f;
    public Transform cameraHolder;
    public float lookSmooth = 10f;

    [Header("Camera Effects")]
    public float headBobAmount = 0.05f;
    public float headBobSpeed = 10f;
    public float swayAmount = 2f;
    public float normalFOV = 60f;
    public float sprintFOV = 70f;
    public float fovSmooth = 8f;

    CharacterController controller;
    Camera cam;
    float xRotation;
    float headBobTimer;
    Vector3 velocity;

    void Start()
    {
        controller = GetComponent<CharacterController>();
        cam = cameraHolder.GetComponentInChildren<Camera>();
        Cursor.lockState = CursorLockMode.Locked;
    }

    void Update()
    {
        HandleMouseLook();
        HandleMovement();
        HandleCameraEffects();
    }

    void HandleMouseLook()
    {
        float mouseX = Input.GetAxis("Mouse X") * mouseSensitivity * Time.deltaTime;
        float mouseY = Input.GetAxis("Mouse Y") * mouseSensitivity * Time.deltaTime;

        xRotation -= mouseY;
        xRotation = Mathf.Clamp(xRotation, -80f, 80f);

        cameraHolder.localRotation = Quaternion.Lerp(
            cameraHolder.localRotation,
            Quaternion.Euler(xRotation, 0f, 0f),
            lookSmooth * Time.deltaTime
        );

        transform.Rotate(Vector3.up * mouseX);
    }

    void HandleMovement()
    {
        float speed = Input.GetKey(KeyCode.LeftShift) ? sprintSpeed : moveSpeed;

        float x = Input.GetAxis("Horizontal");
        float z = Input.GetAxis("Vertical");

        Vector3 move = transform.right * x + transform.forward * z;
        controller.Move(move * speed * Time.deltaTime);

        if (controller.isGrounded && velocity.y < 0)
            velocity.y = -2f;

        velocity.y += gravity * Time.deltaTime;
        controller.Move(velocity * Time.deltaTime);
    }

    void HandleCameraEffects()
    {
        // Head bob
        if (controller.velocity.magnitude > 0.1f && controller.isGrounded)
        {
            headBobTimer += Time.deltaTime * headBobSpeed;
            float bob = Mathf.Sin(headBobTimer) * headBobAmount;
            cameraHolder.localPosition = Vector3.Lerp(
                cameraHolder.localPosition,
                new Vector3(0, bob, 0),
                Time.deltaTime * lookSmooth
            );
        }

        // Camera sway
        float swayX = -Input.GetAxis("Mouse X") * swayAmount;
        float swayY = -Input.GetAxis("Mouse Y") * swayAmount;

        Quaternion swayRotation = Quaternion.Euler(swayY, swayX, 0);
        cameraHolder.localRotation *= swayRotation;

        // FOV kick
        float targetFOV = Input.GetKey(KeyCode.LeftShift) ? sprintFOV : normalFOV;
        cam.fieldOfView = Mathf.Lerp(
            cam.fieldOfView,
            targetFOV,
            Time.deltaTime * fovSmooth
        );
    }
}