//changes which of the canvases is visable
    private void ChangeVisableCanvas()
    {
        //if Reading is the active canvas
        if (listno == 0)
        {
            Reading.GetComponent <Canvas>().enabled = true;
            Q1.GetComponent <Canvas>().enabled      = false;
            Q2.GetComponent <Canvas>().enabled      = false;
            Q3.GetComponent <Canvas>().enabled      = false;
            Q4.GetComponent <Canvas>().enabled      = false;
        }

        //if Q1 is the active canvas
        if (listno == 1)
        {
            Reading.GetComponent <Canvas>().enabled = false;
            Q1.GetComponent <Canvas>().enabled      = true;
            Q2.GetComponent <Canvas>().enabled      = false;
            Q3.GetComponent <Canvas>().enabled      = false;
            Q4.GetComponent <Canvas>().enabled      = false;
        }

        //if Q2 is the active canvas
        if (listno == 2)
        {
            Reading.GetComponent <Canvas>().enabled = false;
            Q1.GetComponent <Canvas>().enabled      = false;
            Q2.GetComponent <Canvas>().enabled      = true;
            Q3.GetComponent <Canvas>().enabled      = false;
            Q4.GetComponent <Canvas>().enabled      = false;
        }

        //if Q3 is the active canvas
        if (listno == 3)
        {
            Reading.GetComponent <Canvas>().enabled = false;
            Q1.GetComponent <Canvas>().enabled      = false;
            Q2.GetComponent <Canvas>().enabled      = false;
            Q3.GetComponent <Canvas>().enabled      = true;
            Q4.GetComponent <Canvas>().enabled      = false;
        }

        //if Q4 is the active canvas
        if (listno >= 4)
        {
            Reading.GetComponent <Canvas>().enabled = false;
            Q1.GetComponent <Canvas>().enabled      = false;
            Q2.GetComponent <Canvas>().enabled      = false;
            Q3.GetComponent <Canvas>().enabled      = false;
            Q4.GetComponent <Canvas>().enabled      = true;
        }
    }