diff --git a/class-Menu.php b/class-Menu.php
index df9838c..38feeda 100644
--- a/class-Menu.php
+++ b/class-Menu.php
@@ -1,109 +1,130 @@
 <?php
-# Copyright (C) 2015, 2019 Valerio Bozzolan
+# Copyright (C) 2015, 2019, 2020 Valerio Bozzolan
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation, either version 3 of the License, or
 # (at your option) any later version.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 /**
- * Handle a menu tree
+ * Menu tree
+ *
+ * This class is useful to store some information
+ * about your menu tree.
  */
 class Menu {
+
+	/**
+	 * All the menu entries
+	 *
+	 * @var array
+	 */
 	private $entries = [];
+
+	/**
+	 * Associative array of 'key' => [ values ] with the tree structure
+	 *
+	 * @var array
+	 */
 	private $tree = [];
+
+	/**
+	 * The menu root UID
+	 *
+	 * @var string
+	 */
 	private $rootUid;
 
 	/**
 	 * Specify the default root identifier.
 	 *
 	 * @param string $rootUid The default menu entry root identifier.
 	 */
 	function __construct( $rootUid = 'root' ) {
 		$this->rootUid = $rootUid;
 	}
 
 	/**
 	 * Get the singleton instance
 	 *
 	 * @return self
 	 */
 	public static function instance() {
 		static $me = false;
-		if( ! $me ) {
+		if( !$me ) {
 			$me = new self();
 		}
 		return $me;
 	}
 
 	/**
 	 * Append a single or an array of menu entries.
 	 *
 	 * @param array|MenuEntry $entries
 	 */
 	public function add( $entries ) {
 		force_array( $entries );
 		foreach( $entries as $menuEntry ) {
 			$this->entries[ $menuEntry->uid ] = $menuEntry;
 			force_array( $menuEntry->parentUid );
 			foreach( $menuEntry->parentUid as $parentUid ) {
 				if( $parentUid === null ) {
 					$parentUid = $this->rootUid;
 				}
 				$this->setParent( $menuEntry->uid, $parentUid );
 			}
 		}
 	}
 
 	/**
 	 * Force a parent->children relation.
 	 *
 	 * @param string $uid Children menu entry identifier.
 	 * @param string $parentUid Parent menu entry identifier.
 	 */
 	public function setParent($uid, $parentUid) {
 		if( ! isset( $this->tree[ $parentUid ] ) || ! is_array( $this->tree[ $parentUid ] ) ) {
 			 $this->tree[ $parentUid ] = [];
 		}
 		$this->tree[ $parentUid ][] = $uid;
 	}
 
 	/**
 	 * Get a single menu entry if registered
 	 *
 	 * @param string $uid Menu entry identifier
 	 * @return MenuEntry
 	 */
 	public function getMenuEntry( $uid ) {
 		if( isset( $this->entries[ $uid ] ) ) {
 			return $this->entries[ $uid ];
 		}
 	}
 
 	/**
 	 * Get an array of menu entries.
 	 *
 	 * @param string|null $parentUid Parent menu entry identifier of the parent. The default menu entry root identifier as default.
 	 * @return array
 	 */
 	public function getChildrenMenuEntries( $parentUid = null ) {
 		if( $parentUid === null ) {
 			$parentUid = $this->rootUid;
 		}
 		$entries = [];
 		if( isset( $this->tree[ $parentUid ] ) ) {
 			foreach( $this->tree[ $parentUid ] as $uid ) {
 				$entries[] = $this->entries[ $uid ];
 			}
 		}
 		return $entries;
 	}
 }