Debug
Debug bar
The skeleton has debugger bar tracy, it allows you to see at a glance various information about your views of your application, the doctrine queries made, the loading of twig, redirections ect...
At the first launch, tracy only displays milliseconds and system info, to display all the information you need click on the icon next to the small cross for a window with a list of checkboxes displayed. Click Toggle All and then press the Set button.
Note that the Console Panel option does not work, and you do not need to check the Eloquent ORM Panel and Idiorm Panel options as we use doctrine.

Debug
To debug during the development of your application, in your controllers/middlewares I recommend using the r() function which is a var_dump improved, but if you want to debug directly on twig you have the function dump() which is enabled when you are in dev development environment.