Create custom admin panel with add_menu_page.txt

add_action('admin_menu', 'create_custom_panel');
function create_custom_panel() {
    add_menu_page('Custom panel', 'Custom panel', 'manage_options', 'custom-panel', 'custom_panel');
}
function custom_panel(){
                echo '<div class="wrap"><div id="icon-options-general" class="icon32">
                        <br>
                </div>
                <h2>Custom panel</h2></div>';
}