public void normal_btn_clicked(GameObject btn_clicked)
    {
        switch (btn_clicked.name)
        {
        case RUN_BTN:
            check_answer(Selected_level_no);
            break;

        case WARNING_OK_BTN:
            Warning_screen.SetActive(false);
            break;

        case ERROR_OK_BTN:
            Wrong_answer_screen.SetActive(false);
            answer_dropdown [Selected_level_no - 1].value = 0;
            break;

        case BACK_BTN_PRGM:
            program_mainscreen.SetActive(false);

            break;

        case BACK_MAIN_PRGM_SCREEN:
            Main_menu_screen.SetActive(true);
            this.gameObject.SetActive(false);
            break;
        }
    }
    public void check_answer(int level_no)
    {
        if (answer_dropdown [level_no - 1].value == correct_answers [level_no - 1])
        {
            success_msg.SetActive(true);
            Output_screen [level_no - 1].SetActive(true);
            switch (Selected_level_no)
            {
            case 1:
                PlayerPrefs.SetInt("prog_1", 1);
                break;

            case 2:
                PlayerPrefs.SetInt("prog_2", 1);
                break;

            case 3:
                PlayerPrefs.SetInt("prog_3", 1);
                break;

            case 4:
                PlayerPrefs.SetInt("prog_4", 1);
                break;

            case 5:
                PlayerPrefs.SetInt("prog_5", 1);
                break;

            case 6:
                PlayerPrefs.SetInt("prog_6", 1);
                break;

            case 7:
                PlayerPrefs.SetInt("prog_7", 1);
                break;

            case 8:
                PlayerPrefs.SetInt("prog_8", 1);
                break;
            }
        }
        else if (answer_dropdown [level_no - 1].value == 0)
        {
            Warning_screen.SetActive(true);
        }
        else
        {
            Wrong_answer_screen.SetActive(true);
        }
    }