c# - Unity 2D How to prevent character from double jump

  private Transform m_GroundCheck;    // A position marking where to check if the player is grounded.
    const float k_GroundedRadius = .2f; // Radius of the overlap circle to determine if grounded
    private bool m_Grounded;            // Whether or not the player is grounded.

    private bool wasGrounded;
    [SerializeField] private float timeToNotGrounded = 0.3f;
    private float timeToNotGroundedTimer;
    private Transform m_CeilingCheck;   // A position marking where to check for ceilings
    const float k_CeilingRadius = .01f; // Radius of the overlap circle to determine if the player can stand up
    private Animator m_Anim;            // Reference to the player's animator component.
    private Rigidbody2D m_Rigidbody2D;
    private bool m_FacingRight = true;  // For determining which way the player is currently facing.




    private void Awake()
    {
        // Setting up references.
        m_GroundCheck = transform.Find("GroundCheck");
        m_CeilingCheck = transform.Find("CeilingCheck");
        m_Anim = GetComponent();
        m_Rigidbody2D = GetComponent();
        timeToNotGroundedTimer = timeToNotGrounded;
    }



    private void FixedUpdate()
    {
        wasGrounded = false;
        // The player is grounded if a circlecast to the groundcheck position hits anything designated as ground
        // This can be done using layers instead but Sample Assets will not overwrite your project settings.
        Collider2D[] colliders = Physics2D.OverlapCircleAll(m_GroundCheck.position, k_GroundedRadius, m_WhatIsGround);
        for (int i = 0; i < colliders.Length; i++)
        {

            if (colliders [i].gameObject != gameObject)
            {
                m_Grounded = true;
                wasGrounded = true;
                timeToNotGroundedTimer = timeToNotGrounded;
            }
        }

        if (!wasGrounded)
        {

            timeToNotGroundedTimer -= Time.fixedDeltaTime;
            if (timeToNotGroundedTimer <= 0)
            {
                Debug.Log ("HAHAHAHA");
                m_Grounded = false;
            }
        }
        m_Anim.SetBool("Ground", m_Grounded);

        // Set the vertical animation

        m_Anim.SetFloat("vSpeed", m_Rigidbody2D.velocity.y);
    }


    public void Move(float move, bool crouch, bool jump)
    {
        // If crouching, check to see if the character can stand up
        if (!crouch && m_Anim.GetBool("Crouch"))
        {
            // If the character has a ceiling preventing them from standing up, keep them crouching

            if (Physics2D.OverlapCircle(m_CeilingCheck.position, k_CeilingRadius, m_WhatIsGround))
            {
                crouch = true;
            }
        }

        // Set whether or not the character is crouching in the animator
        m_Anim.SetBool("Crouch", crouch);

        //only control the player if grounded or airControl is turned on

        if (m_Grounded || m_AirControl)
        {
            // Reduce the speed if crouching by the crouchSpeed multiplier
            move = (crouch ? move*m_CrouchSpeed : move);

            // The Speed animator parameter is set to the absolute value of the horizontal input.
            m_Anim.SetFloat("Speed", Mathf.Abs(move));

            // Move the character
            m_Rigidbody2D.velocity = new Vector2(move*m_MaxSpeed, m_Rigidbody2D.velocity.y);


            // If the input is moving the player right and the player is facing left...
            if (move > 0 && !m_FacingRight)
            {
                // ... flip the player.
                Flip();
            }
                // Otherwise if the input is moving the player left and the player is facing right...
            else if (move < 0 && m_FacingRight)
            {

                // ... flip the player.
                Flip();
            }
        }
        if(jump) Debug.Log (m_Grounded);
        // If the player should jump...
        if (m_Grounded && jump && m_Anim.GetBool("Ground"))
        {               
            // Add a vertical force to the player.
            wasGrounded = false;

            m_Grounded = false;
            m_Anim.SetBool("Ground", false);
            m_Rigidbody2D.velocity = new Vector2 (m_Rigidbody2D.velocity.x, 0);
            m_Rigidbody2D.AddForce(new Vector2(0f, m_JumpForce));
        }
    }

Hi Guys! :D I modified a bit PlatformerCharacter script from Standard Assets from Unity to make it possible to jump in mid air, like here : http://devmag.org.za/2011/01/18/11-tips-for-making-a-fun-platformer/ in point 4. I think everything is okey in code, but my character is double jumping and I can't realize why.