```ruby
class ExercismApp < Sinatra::Base

  get '/:username' do |username|
    please_login
    user = User.where(username: username).first
    if user
      title(user.username)
      erb :user, locals: {user: user, current: user.current_exercises, completed: user.completed_exercises}
    else
      status 404
      erb :not_found
    end
  end

end
```

Make user url case insensitive
user
```ruby
class ExercismApp < Sinatra::Base

  get '/:username' do |username|
    please_login
    user = User.where(username: /\A#{username}\z/i).first

    if user
      title(user.username)
      erb :user, locals: {user: user, current: user.current_exercises, completed: user.completed_exercises}
    else
      status 404
      erb :not_found
    end
  end

end
```
assistant