Untitled

using UnityEngine;

public class CharacterController : MonoBehaviour
{
    public float walkSpeed = 5f;
    public float sprintSpeed = 10f;
    public float jumpForce = 5f;
    public float doubleJumpForce = 7f;
    public Transform groundCheck;
    public LayerMask groundMask;

    private Rigidbody rb;
    private bool isGrounded;
    private bool canDoubleJump;

    void Start()
    {
        rb = GetComponent<Rigidbody>();
    }

    void Update()
    {
        // Check if the character is on the ground
        isGrounded = Physics.CheckSphere(groundCheck.position, 0.2f, groundMask);

        // Walk
        float horizontalInput = Input.GetAxis("Horizontal");
        Vector3 move = transform.right * horizontalInput * walkSpeed;
        rb.velocity = new Vector3(move.x, rb.velocity.y, move.z);

        // Sprint
        if (Input.GetKey(KeyCode.LeftShift))
        {
            move = transform.right * horizontalInput * sprintSpeed;
            rb.velocity = new Vector3(move.x, rb.velocity.y, move.z);
        }

        // Jump
        if (Input.GetButtonDown("Jump"))
        {
            if (isGrounded)
            {
                rb.AddForce(Vector3.up * jumpForce, ForceMode.Impulse);
                canDoubleJump = true;
            }
            else if (canDoubleJump)
            {
                rb.velocity = new Vector3(rb.velocity.x, 0f, rb.velocity.z);
                rb.AddForce(Vector3.up * doubleJumpForce, ForceMode.Impulse);
                canDoubleJump = false;
            }
        }
    }
}