diff --git a/composer.json b/composer.json
index de1bcfb..2dfe2a4 100644
--- a/composer.json
+++ b/composer.json
@@ -43,10 +43,8 @@
         "picocms/composer-installer": "This Composer plugin is responsible for installing Pico plugins and themes using the Composer package manager."
     },
     "autoload": {
-        "psr-0": {
-            "Pico": "lib/",
-            "PicoPluginInterface": "lib/",
-            "AbstractPicoPlugin": "lib/"
+        "psr-4": {
+            "picocms\\Pico\\": "lib/"
         }
     },
     "extra": {
diff --git a/index.php b/index.php
index 0d13d6d..149ffb6 100644
--- a/index.php
+++ b/index.php
@@ -26,7 +26,7 @@ if (is_file(__DIR__ . '/vendor/autoload.php')) {
 }
 
 // instance Pico
-$pico = new Pico(
+$pico = new \picocms\Pico\Pico(
     __DIR__,    // root dir
     'config/',  // config dir
     'plugins/', // plugins dir
diff --git a/index.php.dist b/index.php.dist
index 46c6ddb..7661530 100644
--- a/index.php.dist
+++ b/index.php.dist
@@ -25,7 +25,7 @@ if (!extension_loaded('mbstring')) {
 require_once(__DIR__ . '/vendor/autoload.php');
 
 // instance Pico
-$pico = new Pico(
+$pico = new \picocms\Pico\Pico(
     __DIR__,    // root dir
     'config/',  // config dir
     'plugins/', // plugins dir
diff --git a/lib/AbstractPicoPlugin.php b/lib/AbstractPlugin.php
similarity index 86%
rename from lib/AbstractPicoPlugin.php
rename to lib/AbstractPlugin.php
index 4cc318b..67b632b 100644
--- a/lib/AbstractPicoPlugin.php
+++ b/lib/AbstractPlugin.php
@@ -10,25 +10,27 @@
  * License-Filename: LICENSE
  */
 
+namespace picocms\Pico;
+
 /**
  * Abstract class to extend from when implementing a Pico plugin
  *
- * Please refer to {@see PicoPluginInterface} for more information about how
- * to develop a plugin for Pico.
+ * Please refer to {@see PluginInterface} for more information about how to
+ * develop a plugin for Pico.
  *
- * @see PicoPluginInterface
+ * @see PluginInterface
  *
  * @author  Daniel Rudolf
  * @link    http://picocms.org
  * @license http://opensource.org/licenses/MIT The MIT License
  * @version 3.0
  */
-abstract class AbstractPicoPlugin implements PicoPluginInterface
+abstract class AbstractPlugin implements PluginInterface
 {
     /**
      * Current instance of Pico
      *
-     * @see PicoPluginInterface::getPico()
+     * @see PluginInterface::getPico()
      * @var Pico
      */
     protected $pico;
@@ -36,8 +38,8 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
     /**
      * Boolean indicating if this plugin is enabled (TRUE) or disabled (FALSE)
      *
-     * @see PicoPluginInterface::isEnabled()
-     * @see PicoPluginInterface::setEnabled()
+     * @see PluginInterface::isEnabled()
+     * @see PluginInterface::setEnabled()
      * @var bool|null
      */
     protected $enabled;
@@ -45,7 +47,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
     /**
      * Boolean indicating if this plugin was ever enabled/disabled manually
      *
-     * @see PicoPluginInterface::isStatusChanged()
+     * @see PluginInterface::isStatusChanged()
      * @var bool
      */
     protected $statusChanged = false;
@@ -53,7 +55,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
     /**
      * Boolean indicating whether this plugin matches Pico's API version
      *
-     * @see AbstractPicoPlugin::checkCompatibility()
+     * @see AbstractPlugin::checkCompatibility()
      * @var bool|null
      */
     protected $nativePlugin;
@@ -61,8 +63,8 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
     /**
      * List of plugins which this plugin depends on
      *
-     * @see AbstractPicoPlugin::checkDependencies()
-     * @see PicoPluginInterface::getDependencies()
+     * @see AbstractPlugin::checkDependencies()
+     * @see PluginInterface::getDependencies()
      * @var string[]
      */
     protected $dependsOn = array();
@@ -70,8 +72,8 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
     /**
      * List of plugin which depend on this plugin
      *
-     * @see AbstractPicoPlugin::checkDependants()
-     * @see PicoPluginInterface::getDependants()
+     * @see AbstractPlugin::checkDependants()
+     * @see PluginInterface::getDependants()
      * @var object[]|null
      */
     protected $dependants;
@@ -122,7 +124,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
                 // otherwise the plugin needs to be enabled manually
                 try {
                     $this->setEnabled(true, false, true);
-                } catch (RuntimeException $e) {
+                } catch (\RuntimeException $e) {
                     $this->enabled = false;
                 }
             }
@@ -196,7 +198,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
     /**
      * Passes all not satisfiable method calls to Pico
      *
-     * @see PicoPluginInterface::getPico()
+     * @see PluginInterface::getPico()
      *
      * @deprecated 2.1.0
      *
@@ -211,7 +213,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
             return call_user_func_array(array($this->getPico(), $methodName), $params);
         }
 
-        throw new BadMethodCallException(
+        throw new \BadMethodCallException(
             'Call to undefined method ' . get_class($this->getPico()) . '::' . $methodName . '() '
             . 'through ' . get_called_class() . '::__call()'
         );
@@ -220,37 +222,37 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
     /**
      * Enables all plugins which this plugin depends on
      *
-     * @see PicoPluginInterface::getDependencies()
+     * @see PluginInterface::getDependencies()
      *
      * @param bool $recursive enable required plugins automatically
      *
-     * @throws RuntimeException thrown when a dependency fails
+     * @throws \RuntimeException thrown when a dependency fails
      */
     protected function checkDependencies($recursive)
     {
         foreach ($this->getDependencies() as $pluginName) {
             try {
                 $plugin = $this->getPico()->getPlugin($pluginName);
-            } catch (RuntimeException $e) {
-                throw new RuntimeException(
+            } catch (\RuntimeException $e) {
+                throw new \RuntimeException(
                     "Unable to enable plugin '" . get_called_class() . "': "
                     . "Required plugin '" . $pluginName . "' not found"
                 );
             }
 
             // plugins which don't implement PicoPluginInterface are always enabled
-            if (($plugin instanceof PicoPluginInterface) && !$plugin->isEnabled()) {
+            if (($plugin instanceof PluginInterface) && !$plugin->isEnabled()) {
                 if ($recursive) {
                     if (!$plugin->isStatusChanged()) {
                         $plugin->setEnabled(true, true, true);
                     } else {
-                        throw new RuntimeException(
+                        throw new \RuntimeException(
                             "Unable to enable plugin '" . get_called_class() . "': "
                             . "Required plugin '" . $pluginName . "' was disabled manually"
                         );
                     }
                 } else {
-                    throw new RuntimeException(
+                    throw new \RuntimeException(
                         "Unable to enable plugin '" . get_called_class() . "': "
                         . "Required plugin '" . $pluginName . "' is disabled"
                     );
@@ -270,11 +272,11 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
     /**
      * Disables all plugins which depend on this plugin
      *
-     * @see PicoPluginInterface::getDependants()
+     * @see PluginInterface::getDependants()
      *
      * @param bool $recursive disabled dependant plugins automatically
      *
-     * @throws RuntimeException thrown when a dependency fails
+     * @throws \RuntimeException thrown when a dependency fails
      */
     protected function checkDependants($recursive)
     {
@@ -286,7 +288,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
                         if (!$plugin->isStatusChanged()) {
                             $plugin->setEnabled(false, true, true);
                         } else {
-                            throw new RuntimeException(
+                            throw new \RuntimeException(
                                 "Unable to disable plugin '" . get_called_class() . "': "
                                 . "Required by manually enabled plugin '" . $pluginName . "'"
                             );
@@ -296,7 +298,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
             } else {
                 $dependantsList = 'plugin' . ((count($dependants) > 1) ? 's' : '') . ' '
                     . "'" . implode("', '", array_keys($dependants)) . "'";
-                throw new RuntimeException(
+                throw new \RuntimeException(
                     "Unable to disable plugin '" . get_called_class() . "': "
                     . "Required by " . $dependantsList
                 );
@@ -313,7 +315,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
             $this->dependants = array();
             foreach ($this->getPico()->getPlugins() as $pluginName => $plugin) {
                 // only plugins which implement PicoPluginInterface support dependencies
-                if ($plugin instanceof PicoPluginInterface) {
+                if ($plugin instanceof PluginInterface) {
                     $dependencies = $plugin->getDependencies();
                     if (in_array(get_called_class(), $dependencies)) {
                         $this->dependants[$pluginName] = $plugin;
@@ -335,7 +337,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
      * newer API versions, what requires some special (version specific)
      * precaution and is therefore usually not the case.
      *
-     * @throws RuntimeException thrown when the plugin's and Pico's API aren't
+     * @throws \RuntimeException thrown when the plugin's and Pico's API aren't
      *     compatible
      */
     protected function checkCompatibility()
@@ -348,7 +350,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
             $this->nativePlugin = ($pluginApiVersion === $picoApiVersion);
 
             if (!$this->nativePlugin && ($pluginApiVersion > $picoApiVersion)) {
-                throw new RuntimeException(
+                throw new \RuntimeException(
                     "Unable to enable plugin '" . get_called_class() . "': The plugin's API (version "
                     . $pluginApiVersion . ") isn't compatible with Pico's API (version " . $picoApiVersion . ")"
                 );
diff --git a/lib/Pico.php b/lib/Pico.php
index 6455659..4d82015 100644
--- a/lib/Pico.php
+++ b/lib/Pico.php
@@ -16,6 +16,8 @@
  * License-Filename: LICENSE
  */
 
+namespace picocms\Pico;
+
 /**
  * Pico
  *
@@ -147,7 +149,7 @@ class Pico
     /**
      * List of loaded plugins using the current API version
      *
-     * @var PicoPluginInterface[]
+     * @var PluginInterface[]
      */
     protected $nativePlugins = array();
 
@@ -251,7 +253,7 @@ class Pico
      * Parsedown Extra instance used for markdown parsing
      *
      * @see Pico::getParsedown()
-     * @var Parsedown|null
+     * @var \Parsedown|null
      */
     protected $parsedown;
 
@@ -307,7 +309,7 @@ class Pico
      * Twig instance used for template parsing
      *
      * @see Pico::getTwig()
-     * @var Twig_Environment|null
+     * @var \Twig_Environment|null
      */
     protected $twig;
 
@@ -408,13 +410,13 @@ class Pico
      *
      * @return string rendered Pico contents
      *
-     * @throws Exception thrown when a irrecoverable error occurs
+     * @throws \Exception thrown when a irrecoverable error occurs
      */
     public function run()
     {
         // check lock
         if ($this->locked) {
-            throw new LogicException('You cannot run the same Pico instance multiple times');
+            throw new \LogicException('You cannot run the same Pico instance multiple times');
         }
 
         // lock Pico
@@ -431,7 +433,7 @@ class Pico
 
         // check content dir
         if (!is_dir($this->getConfig('content_dir'))) {
-            throw new RuntimeException('Invalid content directory "' . $this->getConfig('content_dir') . '"');
+            throw new \RuntimeException('Invalid content directory "' . $this->getConfig('content_dir') . '"');
         }
 
         // load theme
@@ -542,7 +544,7 @@ class Pico
      * @see Pico::getPlugin()
      * @see Pico::getPlugins()
      *
-     * @throws RuntimeException thrown when a plugin couldn't be loaded
+     * @throws \RuntimeException thrown when a plugin couldn't be loaded
      */
     protected function loadPlugins()
     {
@@ -553,7 +555,7 @@ class Pico
         }
 
         if (!isset($this->plugins['PicoDeprecated']) && (count($this->plugins) !== count($this->nativePlugins))) {
-            throw new RuntimeException(
+            throw new \RuntimeException(
                 "Plugins using an older API than version " . static::API_VERSION . " found, "
                 . "but PicoDeprecated isn't loaded"
             );
@@ -574,7 +576,7 @@ class Pico
      *
      * @return string[] installer names of the loaded plugins
      *
-     * @throws RuntimeException thrown when a plugin couldn't be loaded
+     * @throws \RuntimeException thrown when a plugin couldn't be loaded
      */
     protected function loadComposerPlugins(array $pluginBlacklist = array())
     {
@@ -601,8 +603,8 @@ class Pico
                     continue;
                 }
 
-                if (!($plugin instanceof PicoPluginInterface)) {
-                    throw new RuntimeException(
+                if (!($plugin instanceof PluginInterface)) {
+                    throw new \RuntimeException(
                         "Unable to load plugin '" . $className . "' via 'vendor/pico-plugin.php': "
                         . "Plugins installed by composer must implement 'PicoPluginInterface'"
                     );
@@ -642,7 +644,7 @@ class Pico
      *
      * @param string[] $pluginBlacklist class names of plugins not to load
      *
-     * @throws RuntimeException thrown when a plugin couldn't be loaded
+     * @throws \RuntimeException thrown when a plugin couldn't be loaded
      */
     protected function loadLocalPlugins(array $pluginBlacklist = array())
     {
@@ -668,7 +670,7 @@ class Pico
                 $pluginFile = $file . '/' . $className . '.php';
 
                 if (!is_file($this->getPluginsDir() . $pluginFile)) {
-                    throw new RuntimeException(
+                    throw new \RuntimeException(
                         "Unable to load plugin '" . $className . "' from '" . $pluginFile . "': File not found"
                     );
                 }
@@ -676,7 +678,7 @@ class Pico
                 $className = preg_replace('/^[0-9]+-/', '', substr($file, 0, -4));
                 $pluginFile = $file;
             } else {
-                throw new RuntimeException("Unable to load plugin from '" . $file . "': Not a valid plugin file");
+                throw new \RuntimeException("Unable to load plugin from '" . $file . "': Not a valid plugin file");
             }
 
             if (isset($this->plugins[$className]) || isset($pluginBlacklist[$className])) {
@@ -692,13 +694,13 @@ class Pico
 
                 $this->plugins[$className] = $plugin;
 
-                if ($plugin instanceof PicoPluginInterface) {
+                if ($plugin instanceof PluginInterface) {
                     if (defined($className . '::API_VERSION') && ($className::API_VERSION >= static::API_VERSION)) {
                         $this->nativePlugins[$className] = $plugin;
                     }
                 }
             } else {
-                throw new RuntimeException(
+                throw new \RuntimeException(
                     "Unable to load plugin '" . $className . "' from '" . $pluginFile . "': Plugin class not found"
                 );
             }
@@ -708,11 +710,11 @@ class Pico
     /**
      * Manually loads a plugin
      *
-     * Manually loaded plugins MUST implement {@see PicoPluginInterface}. They
-     * are simply appended to the plugins array without any additional checks,
-     * so you might get unexpected results, depending on *when* you're loading
-     * a plugin. You SHOULD NOT load plugins after a event has been triggered
-     * by Pico. In-depth knowledge of Pico's inner workings is strongly advised
+     * Manually loaded plugins MUST implement {@see PluginInterface}. They are
+     * simply appended to the plugins array without any additional checks, so
+     * you might get unexpected results, depending on *when* you're loading a
+     * plugin. You SHOULD NOT load plugins after a event has been triggered by
+     * Pico. In-depth knowledge of Pico's inner workings is strongly advised
      * otherwise, and you MUST NOT rely on {@see PicoDeprecated} to maintain
      * backward compatibility in such cases.
      *
@@ -730,12 +732,12 @@ class Pico
      * @see Pico::getPlugin()
      * @see Pico::getPlugins()
      *
-     * @param PicoPluginInterface|string $plugin either the class name of a
-     *     plugin to instantiate or a plugin instance
+     * @param PluginInterface|string $plugin either the class name of a plugin
+     *     to instantiate or a plugin instance
      *
-     * @return PicoPluginInterface instance of the loaded plugin
+     * @return PluginInterface instance of the loaded plugin
      *
-     * @throws RuntimeException thrown when the plugin couldn't be loaded
+     * @throws \RuntimeException thrown when the plugin couldn't be loaded
      */
     public function loadPlugin($plugin)
     {
@@ -744,14 +746,14 @@ class Pico
             if (class_exists($className)) {
                 $plugin = new $className($this);
             } else {
-                throw new RuntimeException("Unable to load plugin '" . $className . "': Class not found");
+                throw new \RuntimeException("Unable to load plugin '" . $className . "': Class not found");
             }
         }
 
         $className = get_class($plugin);
 
-        if (!($plugin instanceof PicoPluginInterface)) {
-            throw new RuntimeException(
+        if (!($plugin instanceof PluginInterface)) {
+            throw new \RuntimeException(
                 "Unable to load plugin '" . $className . "': "
                 . "Manually loaded plugins must implement 'PicoPluginInterface'"
             );
@@ -820,7 +822,7 @@ class Pico
                 $visitedPlugins[$pluginName] = true;
 
                 $dependencies = array();
-                if ($plugin instanceof PicoPluginInterface) {
+                if ($plugin instanceof PluginInterface) {
                     $dependencies = $plugin->getDependencies();
                 }
                 if (!isset($nativePlugins[$pluginName])) {
@@ -857,8 +859,8 @@ class Pico
     /**
      * Returns the instance of a named plugin
      *
-     * Plugins SHOULD implement {@see PicoPluginInterface}, but you MUST NOT
-     * rely on it. For more information see {@see PicoPluginInterface}.
+     * Plugins SHOULD implement {@see PluginInterface}, but you MUST NOT rely
+     * on it. For more information see {@see PluginInterface}.
      *
      * @see Pico::loadPlugins()
      * @see Pico::getPlugins()
@@ -867,7 +869,7 @@ class Pico
      *
      * @return object instance of the plugin
      *
-     * @throws RuntimeException thrown when the plugin wasn't found
+     * @throws \RuntimeException thrown when the plugin wasn't found
      */
     public function getPlugin($pluginName)
     {
@@ -875,7 +877,7 @@ class Pico
             return $this->plugins[$pluginName];
         }
 
-        throw new RuntimeException("Missing plugin '" . $pluginName . "'");
+        throw new \RuntimeException("Missing plugin '" . $pluginName . "'");
     }
 
     /**
@@ -1035,12 +1037,12 @@ class Pico
      *
      * @param array $config array with config variables
      *
-     * @throws LogicException thrown if Pico already started processing
+     * @throws \LogicException thrown if Pico already started processing
      */
     public function setConfig(array $config)
     {
         if ($this->locked) {
-            throw new LogicException("You cannot modify Pico's config after processing has started");
+            throw new \LogicException("You cannot modify Pico's config after processing has started");
         }
 
         $this->config = $config;
@@ -1141,7 +1143,7 @@ class Pico
 
         // check for theme compatibility
         if (!isset($this->plugins['PicoDeprecated']) && ($this->themeApiVersion < static::API_VERSION)) {
-            throw new RuntimeException(
+            throw new \RuntimeException(
                 'Current theme "' . $this->theme . '" uses API version ' . $this->themeApiVersion . ', but Pico '
                 . 'provides API version ' . static::API_VERSION . ' and PicoDeprecated isn\'t loaded'
             );
@@ -1542,12 +1544,12 @@ class Pico
      * This method triggers the `onParsedownRegistered` event when the
      * Parsedown markdown parser wasn't initiated yet.
      *
-     * @return Parsedown Parsedown markdown parser
+     * @return \Parsedown Parsedown markdown parser
      */
     public function getParsedown()
     {
         if ($this->parsedown === null) {
-            $className = $this->config['content_config']['extra'] ? 'ParsedownExtra' : 'Parsedown';
+            $className = $this->config['content_config']['extra'] ? '\ParsedownExtra' : '\Parsedown';
             $this->parsedown = new $className();
 
             $this->parsedown->setBreaksEnabled((bool) $this->config['content_config']['breaks']);
@@ -2075,25 +2077,25 @@ class Pico
      * This method triggers the `onTwigRegistered` event when the Twig template
      * engine wasn't initiated yet. When initiating Twig, this method also
      * registers Pico's core Twig filter `content` as well as Pico's
-     * {@see PicoTwigExtension} Twig extension.
+     * {@see TwigExtension} Twig extension.
      *
      * @see Pico::getTwig()
      * @see http://twig.sensiolabs.org/ Twig website
      * @see https://github.com/twigphp/Twig Twig on GitHub
      *
-     * @return Twig_Environment|null Twig template engine
+     * @return \Twig_Environment|null Twig template engine
      */
     public function getTwig()
     {
         if ($this->twig === null) {
             $twigConfig = $this->getConfig('twig_config');
 
-            $twigLoader = new Twig_Loader_Filesystem($this->getThemesDir() . $this->getTheme());
-            $this->twig = new Twig_Environment($twigLoader, $twigConfig);
-            $this->twig->addExtension(new PicoTwigExtension($this));
+            $twigLoader = new \Twig_Loader_Filesystem($this->getThemesDir() . $this->getTheme());
+            $this->twig = new \Twig_Environment($twigLoader, $twigConfig);
+            $this->twig->addExtension(new TwigExtension($this));
 
             if (!empty($twigConfig['debug'])) {
-                $this->twig->addExtension(new Twig_Extension_Debug());
+                $this->twig->addExtension(new \Twig_Extension_Debug());
             }
 
             // register content filter
@@ -2101,7 +2103,7 @@ class Pico
             // this is the reason why we can't register this filter as part of PicoTwigExtension
             $pico = $this;
             $pages = &$this->pages;
-            $this->twig->addFilter(new Twig_SimpleFilter(
+            $this->twig->addFilter(new \Twig_SimpleFilter(
                 'content',
                 function ($page) use ($pico, &$pages) {
                     if (isset($pages[$page])) {
@@ -2142,7 +2144,7 @@ class Pico
             'theme_url' => $this->getConfig('themes_url') . $this->getTheme(),
             'site_title' => $this->getConfig('site_title'),
             'meta' => $this->meta,
-            'content' => new Twig_Markup($this->content, 'UTF-8'),
+            'content' => new \Twig_Markup($this->content, 'UTF-8'),
             'pages' => $this->pages,
             'previous_page' => $this->previousPage,
             'current_page' => $this->currentPage,
@@ -2281,14 +2283,14 @@ class Pico
      *
      * @return string URL
      *
-     * @throws InvalidArgumentException thrown when invalid arguments got passed
+     * @throws \InvalidArgumentException thrown when invalid arguments got passed
      */
     public function getPageUrl($page, $queryData = null, $dropIndex = true)
     {
         if (is_array($queryData)) {
             $queryData = http_build_query($queryData, '', '&');
         } elseif (($queryData !== null) && !is_string($queryData)) {
-            throw new InvalidArgumentException(
+            throw new \InvalidArgumentException(
                 'Argument 2 passed to ' . __METHOD__ . ' must be of the type array or string, '
                 . (is_object($queryData) ? get_class($queryData) : gettype($queryData)) . ' given'
             );
@@ -2682,7 +2684,7 @@ class Pico
      *
      * @return string normalized path
      *
-     * @throws UnexpectedValueException thrown when a absolute path is passed
+     * @throws \UnexpectedValueException thrown when a absolute path is passed
      *     although absolute paths aren't allowed
      */
     public function getNormalizedPath($path, $allowAbsolutePath = false, $endSlash = true)
@@ -2701,7 +2703,7 @@ class Pico
         }
 
         if ($absolutePath && !$allowAbsolutePath) {
-            throw new UnexpectedValueException(
+            throw new \UnexpectedValueException(
                 'Argument 1 passed to ' . __METHOD__ . ' must be a relative path, absolute path "' . $path . '" given'
             );
         }
@@ -2736,7 +2738,7 @@ class Pico
      * @param string $url      relative or absolute URL
      * @param string $baseUrl  treat relative URLs relative to the given URL;
      *     defaults to Pico::getBaseUrl()
-     * @param bool $endSlash   whether to add a trailing slash to the absolute
+     * @param bool   $endSlash whether to add a trailing slash to the absolute
      *     URL or not (defaults to TRUE)
      *
      * @return string absolute URL
@@ -2761,8 +2763,8 @@ class Pico
      *
      * You MUST NOT trigger events of Pico's core with a plugin!
      *
-     * @see PicoPluginInterface
-     * @see AbstractPicoPlugin
+     * @see PluginInterface
+     * @see AbstractPlugin
      * @see DummyPlugin
      *
      * @param string $eventName name of the event to trigger
diff --git a/lib/PicoPluginInterface.php b/lib/PluginInterface.php
similarity index 91%
rename from lib/PicoPluginInterface.php
rename to lib/PluginInterface.php
index 323be86..ec69745 100644
--- a/lib/PicoPluginInterface.php
+++ b/lib/PluginInterface.php
@@ -10,6 +10,8 @@
  * License-Filename: LICENSE
  */
 
+namespace picocms\Pico;
+
 /**
  * Common interface for Pico plugins
  *
@@ -28,7 +30,7 @@
  * @license http://opensource.org/licenses/MIT The MIT License
  * @version 3.0
  */
-interface PicoPluginInterface
+interface PluginInterface
 {
     /**
      * Handles a event that was triggered by Pico
@@ -41,8 +43,8 @@ interface PicoPluginInterface
     /**
      * Enables or disables this plugin
      *
-     * @see PicoPluginInterface::isEnabled()
-     * @see PicoPluginInterface::isStatusChanged()
+     * @see PluginInterface::isEnabled()
+     * @see PluginInterface::isStatusChanged()
      *
      * @param bool $enabled   enable (TRUE) or disable (FALSE) this plugin
      * @param bool $recursive when TRUE, enable or disable recursively.
@@ -54,7 +56,7 @@ interface PicoPluginInterface
      * @param bool $auto      enable or disable to fulfill a dependency. This
      *     parameter is optional and defaults to FALSE.
      *
-     * @throws RuntimeException thrown when a dependency fails
+     * @throws \RuntimeException thrown when a dependency fails
      */
     public function setEnabled($enabled, $recursive = true, $auto = false);
 
@@ -65,7 +67,7 @@ interface PicoPluginInterface
      * wasn't triggered on all plugins yet. This method might even return NULL
      * then. The plugin's status might change later.
      *
-     * @see PicoPluginInterface::setEnabled()
+     * @see PluginInterface::setEnabled()
      *
      * @return bool|null plugin is enabled (TRUE) or disabled (FALSE)
      */
@@ -74,7 +76,7 @@ interface PicoPluginInterface
     /**
      * Returns TRUE if the plugin was ever enabled/disabled manually
      *
-     * @see PicoPluginInterface::setEnabled()
+     * @see PluginInterface::setEnabled()
      *
      * @return bool plugin is in its default state (TRUE), FALSE otherwise
      */
diff --git a/lib/PicoTwigExtension.php b/lib/TwigExtension.php
similarity index 88%
rename from lib/PicoTwigExtension.php
rename to lib/TwigExtension.php
index d87a6e1..d726191 100644
--- a/lib/PicoTwigExtension.php
+++ b/lib/TwigExtension.php
@@ -10,6 +10,8 @@
  * License-Filename: LICENSE
  */
 
+namespace picocms\Pico;
+
 /**
  * Pico's Twig extension to implement additional filters
  *
@@ -18,12 +20,12 @@
  * @license http://opensource.org/licenses/MIT The MIT License
  * @version 3.0
  */
-class PicoTwigExtension extends Twig_Extension
+class TwigExtension extends \Twig_Extension
 {
     /**
      * Current instance of Pico
      *
-     * @see PicoTwigExtension::getPico()
+     * @see TwigExtension::getPico()
      * @var Pico
      */
     private $pico;
@@ -67,20 +69,20 @@ class PicoTwigExtension extends Twig_Extension
      *
      * @see Twig_ExtensionInterface::getFilters()
      *
-     * @return Twig_SimpleFilter[] array of Pico's Twig filters
+     * @return \Twig_SimpleFilter[] array of Pico's Twig filters
      */
     public function getFilters()
     {
         return array(
-            'markdown' => new Twig_SimpleFilter(
+            'markdown' => new \Twig_SimpleFilter(
                 'markdown',
                 array($this, 'markdownFilter'),
                 array('is_safe' => array('html'))
             ),
-            'map' => new Twig_SimpleFilter('map', array($this, 'mapFilter')),
-            'sort_by' => new Twig_SimpleFilter('sort_by', array($this, 'sortByFilter')),
-            'link' => new Twig_SimpleFilter('link', array($this->pico, 'getPageUrl')),
-            'url' => new Twig_SimpleFilter('url', array($this->pico, 'substituteUrl'))
+            'map' => new \Twig_SimpleFilter('map', array($this, 'mapFilter')),
+            'sort_by' => new \Twig_SimpleFilter('sort_by', array($this, 'sortByFilter')),
+            'link' => new \Twig_SimpleFilter('link', array($this->pico, 'getPageUrl')),
+            'url' => new \Twig_SimpleFilter('url', array($this->pico, 'substituteUrl'))
         );
     }
 
@@ -89,14 +91,14 @@ class PicoTwigExtension extends Twig_Extension
      *
      * @see Twig_ExtensionInterface::getFunctions()
      *
-     * @return Twig_SimpleFunction[] array of Pico's Twig functions
+     * @return \Twig_SimpleFunction[] array of Pico's Twig functions
      */
     public function getFunctions()
     {
         return array(
-            'url_param' => new Twig_SimpleFunction('url_param', array($this, 'urlParamFunction')),
-            'form_param' => new Twig_SimpleFunction('form_param', array($this, 'formParamFunction')),
-            'pages' => new Twig_SimpleFunction('pages', array($this, 'pagesFunction'))
+            'url_param' => new \Twig_SimpleFunction('url_param', array($this, 'urlParamFunction')),
+            'form_param' => new \Twig_SimpleFunction('form_param', array($this, 'formParamFunction')),
+            'pages' => new \Twig_SimpleFunction('pages', array($this, 'pagesFunction'))
         );
     }
 
@@ -129,19 +131,19 @@ class PicoTwigExtension extends Twig_Extension
      * This method is registered as the Twig `map` filter. You can use this
      * filter to e.g. get all page titles (`{{ pages|map("title") }}`).
      *
-     * @param array|Traversable $var        variable to map
-     * @param mixed             $mapKeyPath key to map; either a scalar or a
+     * @param array|\Traversable $var        variable to map
+     * @param mixed              $mapKeyPath key to map; either a scalar or a
      *     array interpreted as key path (i.e. ['foo', 'bar'] will return all
      *     $item['foo']['bar'] values)
      *
      * @return array mapped values
      *
-     * @throws Twig_Error_Runtime
+     * @throws \Twig_Error_Runtime
      */
     public function mapFilter($var, $mapKeyPath)
     {
-        if (!is_array($var) && (!is_object($var) || !($var instanceof Traversable))) {
-            throw new Twig_Error_Runtime(sprintf(
+        if (!is_array($var) && (!is_object($var) || !($var instanceof \Traversable))) {
+            throw new \Twig_Error_Runtime(sprintf(
                 'The map filter only works with arrays or "Traversable", got "%s"',
                 is_object($var) ? get_class($var) : gettype($var)
             ));
@@ -166,11 +168,11 @@ class PicoTwigExtension extends Twig_Extension
      * always sorted in ascending order, apply Twigs `reverse` filter to
      * achieve a descending order.
      *
-     * @param array|Traversable $var         variable to sort
-     * @param mixed             $sortKeyPath key to use for sorting; either
+     * @param array|\Traversable $var         variable to sort
+     * @param mixed              $sortKeyPath key to use for sorting; either
      *     a scalar or a array interpreted as key path (i.e. ['foo', 'bar']
      *     will sort $var by $item['foo']['bar'])
-     * @param string            $fallback    specify what to do with items
+     * @param string             $fallback    specify what to do with items
      *     which don't contain the specified sort key; use "bottom" (default)
      *     to move these items to the end of the sorted array, "top" to rank
      *     them first, "keep" to keep the original order, or "remove" to remove
@@ -178,20 +180,20 @@ class PicoTwigExtension extends Twig_Extension
      *
      * @return array sorted array
      *
-     * @throws Twig_Error_Runtime
+     * @throws \Twig_Error_Runtime
      */
     public function sortByFilter($var, $sortKeyPath, $fallback = 'bottom')
     {
-        if (is_object($var) && ($var instanceof Traversable)) {
+        if (is_object($var) && ($var instanceof \Traversable)) {
             $var = iterator_to_array($var, true);
         } elseif (!is_array($var)) {
-            throw new Twig_Error_Runtime(sprintf(
+            throw new \Twig_Error_Runtime(sprintf(
                 'The sort_by filter only works with arrays or "Traversable", got "%s"',
                 is_object($var) ? get_class($var) : gettype($var)
             ));
         }
         if (($fallback !== 'top') && ($fallback !== 'bottom') && ($fallback !== 'keep') && ($fallback !== "remove")) {
-            throw new Twig_Error_Runtime(
+            throw new \Twig_Error_Runtime(
                 'The sort_by filter only supports the "top", "bottom", "keep" and "remove" fallbacks'
             );
         }
@@ -243,10 +245,10 @@ class PicoTwigExtension extends Twig_Extension
      * Returns the value of a variable item specified by a scalar key or a
      * arbitrary deep sub-key using a key path
      *
-     * @param array|Traversable|ArrayAccess|object $var     base variable
-     * @param mixed                                $keyPath scalar key or a
-     *     array interpreted as key path (when passing e.g. ['foo', 'bar'],
-     *     the method will return $var['foo']['bar']) specifying the value
+     * @param array|\Traversable|\ArrayAccess|object $var     base variable
+     * @param mixed                                  $keyPath scalar key or a
+     *     array interpreted as key path (when passing e.g. ['foo', 'bar'], the
+     *     method will return $var['foo']['bar']) specifying the value
      *
      * @return mixed the requested value or NULL when the given key or key path
      *     didn't match
@@ -261,9 +263,9 @@ class PicoTwigExtension extends Twig_Extension
 
         foreach ($keyPath as $key) {
             if (is_object($var)) {
-                if ($var instanceof ArrayAccess) {
+                if ($var instanceof \ArrayAccess) {
                     // use ArrayAccess, see below
-                } elseif ($var instanceof Traversable) {
+                } elseif ($var instanceof \Traversable) {
                     $var = iterator_to_array($var);
                 } elseif (isset($var->{$key})) {
                     $var = $var->{$key};
@@ -272,7 +274,7 @@ class PicoTwigExtension extends Twig_Extension
                     try {
                         $var = call_user_func(array($var, 'get' . ucfirst($key)));
                         continue;
-                    } catch (BadMethodCallException $e) {
+                    } catch (\BadMethodCallException $e) {
                         return null;
                     }
                 } else {
@@ -421,7 +423,7 @@ class PicoTwigExtension extends Twig_Extension
      *
      * @return array[] the data of the matched pages
      *
-     * @throws Twig_Error_Runtime
+     * @throws \Twig_Error_Runtime
      */
     public function pagesFunction($start = '', $depth = 0, $depthOffset = 0, $offset = 1)
     {
@@ -443,7 +445,7 @@ class PicoTwigExtension extends Twig_Extension
         $depthOffset = $depthOffset + $offset;
 
         if (($depth !== null) && ($depth < 0)) {
-            throw new Twig_Error_Runtime('The pages function doesn\'t support negative depths');
+            throw new \Twig_Error_Runtime('The pages function doesn\'t support negative depths');
         }
 
         $pageTree = $this->getPico()->getPageTree();
diff --git a/plugins/DummyPlugin.php b/plugins/DummyPlugin.php
index 6541f4e..99bf72e 100644
--- a/plugins/DummyPlugin.php
+++ b/plugins/DummyPlugin.php
@@ -10,6 +10,9 @@
  * License-Filename: LICENSE
  */
 
+use picocms\Pico\AbstractPlugin;
+use picocms\Pico\Pico;
+
 /**
  * Pico dummy plugin - a template for plugins
  *
@@ -21,7 +24,7 @@
  * @license http://opensource.org/licenses/MIT The MIT License
  * @version 3.0
  */
-class DummyPlugin extends AbstractPicoPlugin
+class DummyPlugin extends AbstractPlugin
 {
     /**
      * API version used by this plugin
@@ -52,7 +55,7 @@ class DummyPlugin extends AbstractPicoPlugin
      * No matter what, the user can always explicitly enable or disable this
      * plugin in Pico's config.
      *
-     * @see AbstractPicoPlugin::$enabled
+     * @see AbstractPlugin::$enabled
      * @var bool|null
      */
     protected $enabled = false;
@@ -63,7 +66,7 @@ class DummyPlugin extends AbstractPicoPlugin
      * If your plugin doesn't depend on any other plugin, remove this class
      * property.
      *
-     * @see AbstractPicoPlugin::$dependsOn
+     * @see AbstractPlugin::$dependsOn
      * @var string[]
      */
     protected $dependsOn = array();