As user that is looking for something that doesn't exist I want to see a 404 page so that I know it doesn't exist for sure
As user that encountered an unexpected error while using the app I want to see a nice 500 error page so that I know what happended
As a user I want to sign up so that I can start completing my profile and start creating challenges or join other users' challenges
As a user I want to login so that I can continue joining other users' challenges or creating my owns
As a user I want to set up my profile with my favourite sports, etc.