!!!
%html
  %head
    %meta{:content => "text/html; charset=UTF-8", "http-equiv" => "Content-Type"}/

    %title= full_title(yield(:title))

    = stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track' => true
    = javascript_include_tag 'application', 'data-turbolinks-track' => true
    = csrf_meta_tags
    = render 'layouts/shim'

  %body
    = render 'layouts/header'

    .container
      = render 'layouts/flash_message'
      = yield  # contents
      / = render 'layouts/footer'

      - if Rails.env.development?
        = debug(params)
        = render 'layouts/screen_size'

!!!
%html
  %head
    %meta{:content => "text/html; charset=UTF-8", "http-equiv" => "Content-Type"}/
    %meta{:content => "width=device-width, initial-scale=1", :name => "viewport"}/

    %title= full_title(yield(:title))

    = stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track' => true
    = javascript_include_tag 'application', 'data-turbolinks-track' => true
    = csrf_meta_tags
    = render 'layouts/shim'

  %body
    = render 'layouts/header'

    .container
      = render 'layouts/flash_message'
      = yield  # contents
      / = render 'layouts/footer'

      - if Rails.env.development?
        = debug(params)
        = render 'layouts/screen_size'

Add meta-tag for viewport as experiment
Add meta-tag for viewport as experiment
