Just look how easy it is to make all of these responses:

Render a Handlebars template

$app->get('/handlebars-normal', function(){
  echo $GLOBALS['engine']->render('handlebars-example', array(
    'righteous_content' => 'for sure' 
  ));
});

Render a Handlebars template with special STEREO helpers

$app->get('/handlebars-stereo', function(){
  $GLOBALS['app']->render_template(array(
    'template' => 'planets',
    'title' => 'Cool Planets',
    'layout' => false,
    'data' => array(
      'righteous_content' => 'for sure',
      'planets' => array(
        'Mercury', 'Venus', 'Earth', 'Nibiru'
      )
    )
  ));
});

Show a normal php/html document

$app->get('/normal-page', function(){
  require __DIR__ . '/pages/whatever.html';
});

Send an array as JSON for handy API responses

$app->post('/json-response', function(){
  $GLOBALS['app']->render_json(array(
    'righteous_content' => 'for sure'
  ));
});

Set headers, do redirects

$app->get('/whatever', function(){
  header("Location: http://partyphysics.com/");
});

or execute any php code...do literally whatever you want!