xt</div>
    <div class="input_cnt_block">
        <input id="input_checkbox" type="checkbox" />
        <label id="label_for_checkbox" class="label_for_checkbox">Placeholder checkbox text</label>
    </div>
    <button class="button_ok" id="btn_ok">OK</button>
    <script>
        // consts
        var VK_RETURN = 0x0D;
        var VK_SPACE = 0x20;

        // helpers
        var is_closed_manually = false;
        function close_window() {
            is_closed_manually = true;
            window.open('',