float jumpForce = 500f;
    public bool IsJumping { get; set; }

    private bool isGrounded;
    public Transform groundCheck;
    public float checkRadius;
    public LayerMask whatIsGround;



        IsJumping = Input.GetKeyDown (KeyCode.Space);



        if (isGrounded == true)
        {

            if (IsJumping)
            {
                DoJump ();
            }
        }


    public void DoJump ()
    {
        rb.AddForce (Vector2.up * jumpForce);
    }

      isGrounded = Physics2D.OverlapCircle (groundCheck.position, checkRadius, whatIsGround);