<!DOCTYPE html>
<html>
<head>
  <title><%= content_for(:title) or raise "Call content_for :title, 'x'" %></title>
  <%= stylesheet_link_tag    "application", media: "all", "data-turbolinks-track" => true %>
  <%= javascript_include_tag 'vendor', 'application', "data-turbolinks-track" => true %>
  <%= csrf_meta_tags %>
  <%= render 'layouts/google_analytics' %>
</head>
<body class="<%= params[:action] %>">

<%= yield %>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
  <title><%= content_for(:title) or raise "Call content_for :title, 'x'" %></title>
  <%= stylesheet_link_tag    "application", media: "all", "data-turbolinks-track" => true %>
  <%= javascript_include_tag 'vendor', 'application', "data-turbolinks-track" => true %>
  <%= csrf_meta_tags %>

  <%= render 'layouts/google_analytics' %>

  <% if params[:action] == 'menu' %>
    <meta name="viewport" content="width=960">
  <% elsif params[:action] == 'exercise' %>
    <meta name="viewport" content="width=840, minimal-ui">
  <% end %>
</head>
<body class="<%= params[:action] %>">

<%= yield %>

</body>
</html>

Set width and minimal for Mobile Safari
Set width and minimal for Mobile Safari