Usage

Production mode
Limpid, by default, works on development mode that's why you can see the debug barre on the bottom of your screen

The barre shows you the execution time of your script and the number of sql queries
that's why also you see the exception page when something goes wrong like this:

And that's what you get when you go to production mode:

Hmm, so how can I change the 404 page with more elegant one ?
To do this you can create your custom 404 error page and then set it's name in the settings.php file like below:
<?php

return [
. . .
//--error pages manager
'errors' => [
'404' => 'LimpidModule:404error.html.twig',
'500' => '', //'MyModule:500error.html.twig'
],
. . .
];

You can change from development to production mode by changing only one line in one file:
go to app_launcher.php file located on the root of your application folder and open it.
go to line 15 and change this line:
$crossRoadesRouter = new CrossRoadsRooter();
to this one:
$crossRoadesRouter = new CrossRoadsRooter(true);
And that's it, now your application is working on production mode and the debug barre is no longer available.