diff --git a/Gemfile b/Gemfile
index 0099634..f177aa3 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,41 +2,43 @@ source 'https://rubygems.org'
 
 
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
-gem 'rails', '5.1.4'
+gem 'rails', '5.2.2'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3', '~> 1.3.13'
 
-gem 'mysql2', '~> 0.4.10', group: :production
+gem 'mysql2', '~> 0.5.2', group: :production
+
+gem 'bootsnap', require: false
 
 # Use SCSS for stylesheets
-gem 'sass-rails', '~> 5.0.7'
+gem 'sassc-rails', '~> 2.1.0'
 # Use Uglifier as compressor for JavaScript assets
-gem 'uglifier', '~> 3.2.0'
+gem 'uglifier', '~> 4.1.20'
 # Use CoffeeScript for .js.coffee assets and views
 gem 'coffee-rails', '~> 4.2.2'
 # See https://github.com/sstephenson/execjs#readme for more supported runtimes
 # gem 'therubyracer',  platforms: :ruby
 
-gem 'rails-i18n', '~> 5.0.0'
+gem 'rails-i18n', '~> 5.1.3'
 
 gem 'rails-controller-testing'
 
 # Use jquery as the JavaScript library
-gem 'jquery-rails', '~> 4.3.1'
+gem 'jquery-rails', '~> 4.3.3'
 # Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
-gem 'turbolinks', '~> 5.0.1'
+gem 'turbolinks', '~> 5.2.0'
 # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
-gem 'jbuilder', '~> 2.7.0'
+gem 'jbuilder', '~> 2.8.0'
 # bundle exec rake doc:rails generates the API under doc/api.
-gem 'sdoc', '~> 0.4.2',          group: :doc
+gem 'sdoc', '~> 1.0.0',          group: :doc
 
-gem 'web-console', '~> 3.5.1', group: :development
+gem 'web-console', '~> 3.7.0', group: :development
 
 # Use Coveralls for coverage documentation
-gem 'coveralls', '~> 0.8.21', require: false
+gem 'coveralls', '~> 0.8.22', require: false
 
-gem 'bootstrap-sass', '~> 3.3.7'
-gem 'autoprefixer-rails', '~> 7.1.6'
+gem 'bootstrap-sass', '~> 3.4.0'
+gem 'autoprefixer-rails', '~> 9.4.6'
 
 gem 'bh', '~> 1.3.6'
 
@@ -44,9 +46,7 @@ gem 'will_paginate', '~> 3.1.6'
 gem 'will-paginate-i18n', '~> 0.1.15'
 gem 'will_paginate-bootstrap', '~> 1.0.1'
 
-gem 'mathjax-rails', '~> 2.6.1'
-
-gem 'devise', '~> 4.3.0'
+gem 'devise', '~> 4.5.0'
 gem 'devise-bootstrap-views', '~> 0.0.11'
 
 gem 'codemirror-rails', '~> 5.16.0'
@@ -63,4 +63,4 @@ gem 'codemirror-rails', '~> 5.16.0'
 # gem 'debugger', group: [:development, :test]
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
-gem 'tzinfo-data', platforms: [:mingw, :mswin]
+gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw]
diff --git a/Gemfile.lock b/Gemfile.lock
index 07b88fc..53dd765 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,55 +1,62 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    actioncable (5.1.4)
-      actionpack (= 5.1.4)
+    actioncable (5.2.2)
+      actionpack (= 5.2.2)
       nio4r (~> 2.0)
-      websocket-driver (~> 0.6.1)
-    actionmailer (5.1.4)
-      actionpack (= 5.1.4)
-      actionview (= 5.1.4)
-      activejob (= 5.1.4)
+      websocket-driver (>= 0.6.1)
+    actionmailer (5.2.2)
+      actionpack (= 5.2.2)
+      actionview (= 5.2.2)
+      activejob (= 5.2.2)
       mail (~> 2.5, >= 2.5.4)
       rails-dom-testing (~> 2.0)
-    actionpack (5.1.4)
-      actionview (= 5.1.4)
-      activesupport (= 5.1.4)
+    actionpack (5.2.2)
+      actionview (= 5.2.2)
+      activesupport (= 5.2.2)
       rack (~> 2.0)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.2)
-    actionview (5.1.4)
-      activesupport (= 5.1.4)
+    actionview (5.2.2)
+      activesupport (= 5.2.2)
       builder (~> 3.1)
       erubi (~> 1.4)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.3)
-    activejob (5.1.4)
-      activesupport (= 5.1.4)
+    activejob (5.2.2)
+      activesupport (= 5.2.2)
       globalid (>= 0.3.6)
-    activemodel (5.1.4)
-      activesupport (= 5.1.4)
-    activerecord (5.1.4)
-      activemodel (= 5.1.4)
-      activesupport (= 5.1.4)
-      arel (~> 8.0)
-    activesupport (5.1.4)
+    activemodel (5.2.2)
+      activesupport (= 5.2.2)
+    activerecord (5.2.2)
+      activemodel (= 5.2.2)
+      activesupport (= 5.2.2)
+      arel (>= 9.0)
+    activestorage (5.2.2)
+      actionpack (= 5.2.2)
+      activerecord (= 5.2.2)
+      marcel (~> 0.3.1)
+    activesupport (5.2.2)
       concurrent-ruby (~> 1.0, >= 1.0.2)
-      i18n (~> 0.7)
+      i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-    arel (8.0.0)
-    autoprefixer-rails (7.1.6)
+    arel (9.0.0)
+    autoprefixer-rails (9.4.6)
       execjs
-    bcrypt (3.1.11)
-    bcrypt (3.1.11-x86-mingw32)
+    bcrypt (3.1.12)
+    bcrypt (3.1.12-x64-mingw32)
+    bcrypt (3.1.12-x86-mingw32)
     bh (1.3.6)
       actionpack
       activesupport
     bindex (0.5.0)
-    bootstrap-sass (3.3.7)
+    bootsnap (1.3.2)
+      msgpack (~> 1.0)
+    bootstrap-sass (3.4.0)
       autoprefixer-rails (>= 5.2.1)
-      sass (>= 3.3.4)
+      sassc (>= 2.0.0)
     builder (3.2.3)
     codemirror-rails (5.16.0)
       railties (>= 3.0, < 6.0)
@@ -60,140 +67,154 @@ GEM
       coffee-script-source
       execjs
     coffee-script-source (1.12.2)
-    concurrent-ruby (1.0.5)
-    coveralls (0.8.21)
+    concurrent-ruby (1.1.4)
+    coveralls (0.8.22)
       json (>= 1.8, < 3)
-      simplecov (~> 0.14.1)
+      simplecov (~> 0.16.1)
       term-ansicolor (~> 1.3)
       thor (~> 0.19.4)
       tins (~> 1.6)
-    crass (1.0.3)
-    devise (4.3.0)
+    crass (1.0.4)
+    devise (4.5.0)
       bcrypt (~> 3.0)
       orm_adapter (~> 0.1)
-      railties (>= 4.1.0, < 5.2)
+      railties (>= 4.1.0, < 6.0)
       responders
       warden (~> 1.2.3)
     devise-bootstrap-views (0.0.11)
-    docile (1.1.5)
-    erubi (1.7.0)
+    docile (1.3.1)
+    erubi (1.8.0)
     execjs (2.7.0)
-    globalid (0.4.1)
+    ffi (1.9.25)
+    ffi (1.9.25-x64-mingw32)
+    ffi (1.9.25-x86-mingw32)
+    globalid (0.4.2)
       activesupport (>= 4.2.0)
-    i18n (0.9.1)
+    i18n (0.9.5)
       concurrent-ruby (~> 1.0)
-    jbuilder (2.7.0)
+    jbuilder (2.8.0)
       activesupport (>= 4.2.0)
       multi_json (>= 1.2)
-    jquery-rails (4.3.1)
+    jquery-rails (4.3.3)
       rails-dom-testing (>= 1, < 3)
       railties (>= 4.2.0)
       thor (>= 0.14, < 2.0)
     json (1.8.6)
-    loofah (2.1.1)
+    loofah (2.2.3)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
-    mail (2.7.0)
+    mail (2.7.1)
       mini_mime (>= 0.1.1)
-    mathjax-rails (2.6.1)
-      railties (>= 3.0)
-    method_source (0.9.0)
-    mini_mime (1.0.0)
-    mini_portile2 (2.3.0)
-    minitest (5.10.3)
-    multi_json (1.12.2)
-    mysql2 (0.4.10)
-    mysql2 (0.4.10-x86-mingw32)
-    nio4r (2.1.0)
-    nokogiri (1.8.1)
-      mini_portile2 (~> 2.3.0)
-    nokogiri (1.8.1-x86-mingw32)
-      mini_portile2 (~> 2.3.0)
+    marcel (0.3.3)
+      mimemagic (~> 0.3.2)
+    method_source (0.9.2)
+    mimemagic (0.3.3)
+    mini_mime (1.0.1)
+    mini_portile2 (2.4.0)
+    minitest (5.11.3)
+    msgpack (1.2.6)
+    msgpack (1.2.6-x64-mingw32)
+    msgpack (1.2.6-x86-mingw32)
+    multi_json (1.13.1)
+    mysql2 (0.5.2)
+    mysql2 (0.5.2-x64-mingw32)
+    mysql2 (0.5.2-x86-mingw32)
+    nio4r (2.3.1)
+    nokogiri (1.10.1)
+      mini_portile2 (~> 2.4.0)
+    nokogiri (1.10.1-x64-mingw32)
+      mini_portile2 (~> 2.4.0)
+    nokogiri (1.10.1-x86-mingw32)
+      mini_portile2 (~> 2.4.0)
     orm_adapter (0.5.0)
-    rack (2.0.3)
-    rack-test (0.8.2)
+    rack (2.0.6)
+    rack-test (1.1.0)
       rack (>= 1.0, < 3)
-    rails (5.1.4)
-      actioncable (= 5.1.4)
-      actionmailer (= 5.1.4)
-      actionpack (= 5.1.4)
-      actionview (= 5.1.4)
-      activejob (= 5.1.4)
-      activemodel (= 5.1.4)
-      activerecord (= 5.1.4)
-      activesupport (= 5.1.4)
+    rails (5.2.2)
+      actioncable (= 5.2.2)
+      actionmailer (= 5.2.2)
+      actionpack (= 5.2.2)
+      actionview (= 5.2.2)
+      activejob (= 5.2.2)
+      activemodel (= 5.2.2)
+      activerecord (= 5.2.2)
+      activestorage (= 5.2.2)
+      activesupport (= 5.2.2)
       bundler (>= 1.3.0)
-      railties (= 5.1.4)
+      railties (= 5.2.2)
       sprockets-rails (>= 2.0.0)
-    rails-controller-testing (1.0.2)
-      actionpack (~> 5.x, >= 5.0.1)
-      actionview (~> 5.x, >= 5.0.1)
-      activesupport (~> 5.x)
+    rails-controller-testing (1.0.4)
+      actionpack (>= 5.0.1.x)
+      actionview (>= 5.0.1.x)
+      activesupport (>= 5.0.1.x)
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.0.3)
-      loofah (~> 2.0)
-    rails-i18n (5.0.4)
-      i18n (~> 0.7)
-      railties (~> 5.0)
-    railties (5.1.4)
-      actionpack (= 5.1.4)
-      activesupport (= 5.1.4)
+    rails-html-sanitizer (1.0.4)
+      loofah (~> 2.2, >= 2.2.2)
+    rails-i18n (5.1.3)
+      i18n (>= 0.7, < 2)
+      railties (>= 5.0, < 6)
+    railties (5.2.2)
+      actionpack (= 5.2.2)
+      activesupport (= 5.2.2)
       method_source
       rake (>= 0.8.7)
-      thor (>= 0.18.1, < 2.0)
-    rake (12.3.0)
-    rdoc (4.3.0)
-    responders (2.4.0)
-      actionpack (>= 4.2.0, < 5.3)
-      railties (>= 4.2.0, < 5.3)
-    sass (3.4.19)
-    sass-rails (5.0.7)
-      railties (>= 4.0.0, < 6)
-      sass (~> 3.1)
-      sprockets (>= 2.8, < 4.0)
-      sprockets-rails (>= 2.0, < 4.0)
-      tilt (>= 1.1, < 3)
-    sdoc (0.4.2)
-      json (~> 1.7, >= 1.7.7)
-      rdoc (~> 4.0)
-    simplecov (0.14.1)
-      docile (~> 1.1.0)
+      thor (>= 0.19.0, < 2.0)
+    rake (12.3.2)
+    rdoc (6.1.1)
+    responders (2.4.1)
+      actionpack (>= 4.2.0, < 6.0)
+      railties (>= 4.2.0, < 6.0)
+    sassc (2.0.0)
+      ffi (~> 1.9.6)
+      rake
+    sassc-rails (2.1.0)
+      railties (>= 4.0.0)
+      sassc (>= 2.0)
+      sprockets (> 3.0)
+      sprockets-rails
+      tilt
+    sdoc (1.0.0)
+      rdoc (>= 5.0)
+    simplecov (0.16.1)
+      docile (~> 1.1)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    sprockets (3.4.1)
+    sprockets (3.7.2)
+      concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
-    sprockets-rails (2.3.3)
-      actionpack (>= 3.0)
-      activesupport (>= 3.0)
-      sprockets (>= 2.8, < 4.0)
+    sprockets-rails (3.2.1)
+      actionpack (>= 4.0)
+      activesupport (>= 4.0)
+      sprockets (>= 3.0.0)
     sqlite3 (1.3.13)
+    sqlite3 (1.3.13-x64-mingw32)
     sqlite3 (1.3.13-x86-mingw32)
-    term-ansicolor (1.6.0)
+    term-ansicolor (1.7.1)
       tins (~> 1.0)
     thor (0.19.4)
     thread_safe (0.3.6)
-    tilt (2.0.8)
-    tins (1.15.1)
-    turbolinks (5.0.1)
-      turbolinks-source (~> 5)
-    turbolinks-source (5.0.3)
-    tzinfo (1.2.4)
+    tilt (2.0.9)
+    tins (1.20.2)
+    turbolinks (5.2.0)
+      turbolinks-source (~> 5.2)
+    turbolinks-source (5.2.0)
+    tzinfo (1.2.5)
       thread_safe (~> 0.1)
-    tzinfo-data (1.2015.7)
+    tzinfo-data (1.2018.9)
       tzinfo (>= 1.0.0)
-    uglifier (3.2.0)
+    uglifier (4.1.20)
       execjs (>= 0.3.0, < 3)
-    warden (1.2.7)
-      rack (>= 1.0)
-    web-console (3.5.1)
+    warden (1.2.8)
+      rack (>= 2.0.6)
+    web-console (3.7.0)
       actionview (>= 5.0)
       activemodel (>= 5.0)
       bindex (>= 0.4.0)
       railties (>= 5.0)
-    websocket-driver (0.6.5)
+    websocket-driver (0.7.0)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.3)
     will-paginate-i18n (0.1.15)
@@ -203,34 +224,35 @@ GEM
 
 PLATFORMS
   ruby
+  x64-mingw32
   x86-mingw32
 
 DEPENDENCIES
-  autoprefixer-rails (~> 7.1.6)
+  autoprefixer-rails (~> 9.4.6)
   bh (~> 1.3.6)
-  bootstrap-sass (~> 3.3.7)
+  bootsnap
+  bootstrap-sass (~> 3.4.0)
   codemirror-rails (~> 5.16.0)
   coffee-rails (~> 4.2.2)
-  coveralls (~> 0.8.21)
-  devise (~> 4.3.0)
+  coveralls (~> 0.8.22)
+  devise (~> 4.5.0)
   devise-bootstrap-views (~> 0.0.11)
-  jbuilder (~> 2.7.0)
-  jquery-rails (~> 4.3.1)
-  mathjax-rails (~> 2.6.1)
-  mysql2 (~> 0.4.10)
-  rails (= 5.1.4)
+  jbuilder (~> 2.8.0)
+  jquery-rails (~> 4.3.3)
+  mysql2 (~> 0.5.2)
+  rails (= 5.2.2)
   rails-controller-testing
-  rails-i18n (~> 5.0.0)
-  sass-rails (~> 5.0.7)
-  sdoc (~> 0.4.2)
+  rails-i18n (~> 5.1.3)
+  sassc-rails (~> 2.1.0)
+  sdoc (~> 1.0.0)
   sqlite3 (~> 1.3.13)
-  turbolinks (~> 5.0.1)
+  turbolinks (~> 5.2.0)
   tzinfo-data
-  uglifier (~> 3.2.0)
-  web-console (~> 3.5.1)
+  uglifier (~> 4.1.20)
+  web-console (~> 3.7.0)
   will-paginate-i18n (~> 0.1.15)
   will_paginate (~> 3.1.6)
   will_paginate-bootstrap (~> 1.0.1)
 
 BUNDLED WITH
-   1.16.0
+   1.17.2
diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index ecb6882..502bbac 100644
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -16,7 +16,7 @@
       "HTML-CSS": { availableFonts: ["TeX"] }
     });
   </script>
-  <%= mathjax_tag config: 'TeX-AMS_HTML' %>
+  <script src='https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-AMS_HTML' async></script>
   <%= csrf_meta_tags %>
 </head>
 <body>
diff --git a/bin/bundle b/bin/bundle
index e3c2f62..8d5f7a5 100644
--- a/bin/bundle
+++ b/bin/bundle
@@ -1,3 +1,3 @@
 #!/usr/bin/env ruby.exe
-ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)
+ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
 load Gem.bin_path('bundler', 'bundle')
diff --git a/bin/setup b/bin/setup
index 00ad3ec..237a371 100644
--- a/bin/setup
+++ b/bin/setup
@@ -1,10 +1,9 @@
 #!/usr/bin/env ruby.exe
-require 'pathname'
 require 'fileutils'
 include FileUtils
 
 # path to your application root.
-APP_ROOT = Pathname.new File.expand_path('../../', __FILE__)
+APP_ROOT = File.expand_path('..', __dir__)
 
 def system!(*args)
   system(*args) || abort("\n== Command #{args} failed ==")
@@ -21,7 +20,6 @@ chdir APP_ROOT do
   # Install JavaScript dependencies if using Yarn
   # system('bin/yarn')
 
-
   # puts "\n== Copying sample files =="
   # unless File.exist?('config/database.yml')
   #   cp 'config/database.yml.sample', 'config/database.yml'
diff --git a/bin/update b/bin/update
index deb1df2..1db4ab5 100644
--- a/bin/update
+++ b/bin/update
@@ -1,10 +1,9 @@
 #!/usr/bin/env ruby.exe
-require 'pathname'
 require 'fileutils'
 include FileUtils
 
 # path to your application root.
-APP_ROOT = Pathname.new File.expand_path('../../', __FILE__)
+APP_ROOT = File.expand_path('..', __dir__)
 
 def system!(*args)
   system(*args) || abort("\n== Command #{args} failed ==")
@@ -18,6 +17,9 @@ chdir APP_ROOT do
   system! 'gem install bundler --conservative'
   system('bundle check') || system!('bundle install')
 
+  # Install JavaScript dependencies if using Yarn
+  # system('bin/yarn')
+
   puts "\n== Updating database =="
   system! 'bin/rails db:migrate'
 
diff --git a/bin/yarn b/bin/yarn
index 07471fe..3389822 100644
--- a/bin/yarn
+++ b/bin/yarn
@@ -1,8 +1,8 @@
 #!/usr/bin/env ruby.exe
-VENDOR_PATH = File.expand_path('..', __dir__)
-Dir.chdir(VENDOR_PATH) do
+APP_ROOT = File.expand_path('..', __dir__)
+Dir.chdir(APP_ROOT) do
   begin
-    exec "yarnpkg #{ARGV.join(" ")}"
+    exec "yarnpkg", *ARGV
   rescue Errno::ENOENT
     $stderr.puts "Yarn executable was not detected in the system."
     $stderr.puts "Download Yarn at https://yarnpkg.com/en/docs/install"
diff --git a/config/application.rb b/config/application.rb
index e5e1434..b4c1e2b 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -9,11 +9,12 @@ Bundler.require(*Rails.groups)
 module Projekteuler
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
-    config.load_defaults 5.1
+    config.load_defaults 5.2
 
     # Settings in config/environments/* take precedence over those specified here.
-    # Application configuration should go into files in config/initializers
-    # -- all .rb files in that directory are automatically loaded.
+    # Application configuration can go into files in config/initializers
+    # -- all .rb files in that directory are automatically loaded after loading
+    # the framework and any gems in your application.
 
     # Set Time.zone default to the specified zone and make Active Record auto-convert to this zone.
     # Run "rake -D time" for a list of tasks for finding time zone names. Default is UTC.
diff --git a/config/boot.rb b/config/boot.rb
index 30f5120..b9e460c 100644
--- a/config/boot.rb
+++ b/config/boot.rb
@@ -1,3 +1,4 @@
 ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
 
 require 'bundler/setup' # Set up gems listed in the Gemfile.
+require 'bootsnap/setup' # Speed up boot time by caching expensive operations.
diff --git a/config/cable.yml b/config/cable.yml
index 4ff27ac..0c84e98 100644
--- a/config/cable.yml
+++ b/config/cable.yml
@@ -6,5 +6,5 @@ test:
 
 production:
   adapter: redis
-  url: redis://localhost:6379/1
+  url: <%= ENV.fetch("REDIS_URL") { "redis://localhost:6379/1" } %>
   channel_prefix: projekteuler_production
diff --git a/config/environments/development.rb b/config/environments/development.rb
index c6e62d1..8a3fed0 100644
--- a/config/environments/development.rb
+++ b/config/environments/development.rb
@@ -13,12 +13,13 @@ Rails.application.configure do
   config.consider_all_requests_local = true
 
   # Enable/disable caching. By default caching is disabled.
-  if Rails.root.join('tmp/caching-dev.txt').exist?
+  # Run rails dev:cache to toggle caching.
+  if Rails.root.join('tmp', 'caching-dev.txt').exist?
     config.action_controller.perform_caching = true
 
     config.cache_store = :memory_store
     config.public_file_server.headers = {
-      'Cache-Control' => "public, max-age=#{2.days.seconds.to_i}"
+      'Cache-Control' => "public, max-age=#{2.days.to_i}"
     }
   else
     config.action_controller.perform_caching = false
@@ -26,6 +27,9 @@ Rails.application.configure do
     config.cache_store = :null_store
   end
 
+  # Store uploaded files on the local file system (see config/storage.yml for options)
+  config.active_storage.service = :local
+
   # Don't care if the mailer can't send.
   config.action_mailer.raise_delivery_errors = false
 
@@ -37,6 +41,9 @@ Rails.application.configure do
   # Raise an error on page load if there are pending migrations.
   config.active_record.migration_error = :page_load
 
+  # Highlight code that triggered database queries in logs.
+  config.active_record.verbose_query_logs = true
+
   # Debug mode disables concatenation and preprocessing of assets.
   # This option may cause significant delays in view rendering with a large
   # number of complex assets.
diff --git a/config/environments/production.rb b/config/environments/production.rb
index cd32635..7312a67 100644
--- a/config/environments/production.rb
+++ b/config/environments/production.rb
@@ -14,10 +14,9 @@ Rails.application.configure do
   config.consider_all_requests_local       = false
   config.action_controller.perform_caching = true
 
-  # Attempt to read encrypted secrets from `config/secrets.yml.enc`.
-  # Requires an encryption key in `ENV["RAILS_MASTER_KEY"]` or
-  # `config/secrets.yml.key`.
-  config.read_encrypted_secrets = true
+  # Ensures that a master key has been made available in either ENV["RAILS_MASTER_KEY"]
+  # or in config/master.key. This key is used to decrypt credentials (and other encrypted files).
+  config.require_master_key = true
 
   # Disable serving static files from the `/public` folder by default since
   # Apache or NGINX already handles this.
@@ -30,8 +29,6 @@ Rails.application.configure do
   # Do not fallback to assets pipeline if a precompiled asset is missed.
   config.assets.compile = false
 
-  config.assets.digest = true
-
   # `config.assets.precompile` and `config.assets.version` have moved to config/initializers/assets.rb
 
   # Enable serving of images, stylesheets, and JavaScripts from an asset server.
@@ -41,6 +38,9 @@ Rails.application.configure do
   # config.action_dispatch.x_sendfile_header = 'X-Sendfile' # for Apache
   # config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for NGINX
 
+  # Store uploaded files on the local file system (see config/storage.yml for options)
+  config.active_storage.service = :local
+
   # Mount Action Cable outside main process or domain
   # config.action_cable.mount_path = nil
   # config.action_cable.url = 'wss://example.com/cable'
@@ -62,6 +62,7 @@ Rails.application.configure do
   # Use a real queuing backend for Active Job (and separate queues per environment)
   # config.active_job.queue_adapter     = :resque
   # config.active_job.queue_name_prefix = "projekteuler_#{Rails.env}"
+
   config.action_mailer.perform_caching = false
 
   # Ignore bad email addresses and do not raise email delivery errors.
diff --git a/config/environments/test.rb b/config/environments/test.rb
index 4fc9260..9f71b93 100644
--- a/config/environments/test.rb
+++ b/config/environments/test.rb
@@ -15,7 +15,7 @@ Rails.application.configure do
   # Configure public file server for tests with Cache-Control for performance.
   config.public_file_server.enabled = true
   config.public_file_server.headers = {
-    'Cache-Control' => "public, max-age=#{1.hour.seconds.to_i}"
+    'Cache-Control' => "public, max-age=#{1.hour.to_i}"
   }
 
   # Show full error reports and disable caching.
@@ -27,6 +27,10 @@ Rails.application.configure do
 
   # Disable request forgery protection in test environment.
   config.action_controller.allow_forgery_protection = false
+
+  # Store uploaded files on the local file system in a temporary directory
+  config.active_storage.service = :test
+
   config.action_mailer.perform_caching = false
 
   # Tell Action Mailer not to deliver emails to the real world.
diff --git a/config/initializers/content_security_policy.rb b/config/initializers/content_security_policy.rb
new file mode 100644
index 0000000..d3bcaa5
--- /dev/null
+++ b/config/initializers/content_security_policy.rb
@@ -0,0 +1,25 @@
+# Be sure to restart your server when you modify this file.
+
+# Define an application-wide content security policy
+# For further information see the following documentation
+# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
+
+# Rails.application.config.content_security_policy do |policy|
+#   policy.default_src :self, :https
+#   policy.font_src    :self, :https, :data
+#   policy.img_src     :self, :https, :data
+#   policy.object_src  :none
+#   policy.script_src  :self, :https
+#   policy.style_src   :self, :https
+
+#   # Specify URI for violation reports
+#   # policy.report_uri "/csp-violation-report-endpoint"
+# end
+
+# If you are using UJS then enable automatic nonce generation
+# Rails.application.config.content_security_policy_nonce_generator = -> request { SecureRandom.base64(16) }
+
+# Report CSP violations to a specified URI
+# For further information see the following documentation:
+# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only
+# Rails.application.config.content_security_policy_report_only = true
diff --git a/config/routes.rb b/config/routes.rb
index 27b3c81..49fc368 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -1,4 +1,12 @@
 Rails.application.routes.draw do
+  # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
+
+  # The priority is based upon order of creation: first created -> highest priority.
+  # See how all your routes lay out with "rake routes".
+
+  # You can have the root of your site routed with "root"
+  root 'about#index'
+
   get 'about/index'
   get 'about/info'
   get 'about/copyright'
@@ -20,62 +28,4 @@ Rails.application.routes.draw do
     post '/update_problem_count', to: 'dashboard#update_problem_count', as: 'dashboard_update_problem_count'
     resources :translations, only: [:index, :show]
   end
-
-  mathjax 'mathjax'
-
-  # The priority is based upon order of creation: first created -> highest priority.
-  # See how all your routes lay out with "rake routes".
-
-  # You can have the root of your site routed with "root"
-  root 'about#index'
-
-  # Example of regular route:
-  #   get 'products/:id' => 'catalog#view'
-
-  # Example of named route that can be invoked with purchase_url(id: product.id)
-  #   get 'products/:id/purchase' => 'catalog#purchase', as: :purchase
-
-  # Example resource route (maps HTTP verbs to controller actions automatically):
-  #   resources :products
-
-  # Example resource route with options:
-  #   resources :products do
-  #     member do
-  #       get 'short'
-  #       post 'toggle'
-  #     end
-  #
-  #     collection do
-  #       get 'sold'
-  #     end
-  #   end
-
-  # Example resource route with sub-resources:
-  #   resources :products do
-  #     resources :comments, :sales
-  #     resource :seller
-  #   end
-
-  # Example resource route with more complex sub-resources:
-  #   resources :products do
-  #     resources :comments
-  #     resources :sales do
-  #       get 'recent', on: :collection
-  #     end
-  #   end
-
-  # Example resource route with concerns:
-  #   concern :toggleable do
-  #     post 'toggle'
-  #   end
-  #   resources :posts, concerns: :toggleable
-  #   resources :photos, concerns: :toggleable
-
-  # Example resource route within a namespace:
-  #   namespace :admin do
-  #     # Directs /admin/products/* to Admin::ProductsController
-  #     # (app/controllers/admin/products_controller.rb)
-  #     resources :products
-  #   end
-  # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
-end
+end
\ No newline at end of file
diff --git a/config/storage.yml b/config/storage.yml
new file mode 100644
index 0000000..d32f76e
--- /dev/null
+++ b/config/storage.yml
@@ -0,0 +1,34 @@
+test:
+  service: Disk
+  root: <%= Rails.root.join("tmp/storage") %>
+
+local:
+  service: Disk
+  root: <%= Rails.root.join("storage") %>
+
+# Use rails credentials:edit to set the AWS secrets (as aws:access_key_id|secret_access_key)
+# amazon:
+#   service: S3
+#   access_key_id: <%= Rails.application.credentials.dig(:aws, :access_key_id) %>
+#   secret_access_key: <%= Rails.application.credentials.dig(:aws, :secret_access_key) %>
+#   region: us-east-1
+#   bucket: your_own_bucket
+
+# Remember not to checkin your GCS keyfile to a repository
+# google:
+#   service: GCS
+#   project: your_project
+#   credentials: <%= Rails.root.join("path/to/gcs.keyfile") %>
+#   bucket: your_own_bucket
+
+# Use rails credentials:edit to set the Azure Storage secret (as azure_storage:storage_access_key)
+# microsoft:
+#   service: AzureStorage
+#   storage_account_name: your_account_name
+#   storage_access_key: <%= Rails.application.credentials.dig(:azure_storage, :storage_access_key) %>
+#   container: your_container_name
+
+# mirror:
+#   service: Mirror
+#   primary: local
+#   mirrors: [ amazon, google, microsoft ]
diff --git a/db/schema.rb b/db/schema.rb
index ee93b97..3475fce 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -1,4 +1,3 @@
-# encoding: UTF-8
 # This file is auto-generated from the current state of the database. Instead
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.
@@ -14,39 +13,36 @@
 ActiveRecord::Schema.define(version: 20150131103802) do
 
   create_table "admins", force: :cascade do |t|
-    t.string   "email",                  default: "", null: false
-    t.string   "encrypted_password",     default: "", null: false
-    t.string   "reset_password_token"
+    t.string "email", default: "", null: false
+    t.string "encrypted_password", default: "", null: false
+    t.string "reset_password_token"
     t.datetime "reset_password_sent_at"
     t.datetime "remember_created_at"
-    t.integer  "sign_in_count",          default: 0,  null: false
+    t.integer "sign_in_count", default: 0, null: false
     t.datetime "current_sign_in_at"
     t.datetime "last_sign_in_at"
-    t.string   "current_sign_in_ip"
-    t.string   "last_sign_in_ip"
+    t.string "current_sign_in_ip"
+    t.string "last_sign_in_ip"
     t.datetime "created_at"
     t.datetime "updated_at"
+    t.index ["email"], name: "index_admins_on_email", unique: true
+    t.index ["reset_password_token"], name: "index_admins_on_reset_password_token", unique: true
   end
 
-  add_index "admins", ["email"], name: "index_admins_on_email", unique: true
-  add_index "admins", ["reset_password_token"], name: "index_admins_on_reset_password_token", unique: true
-
   create_table "problems", force: :cascade do |t|
     t.datetime "created_at"
     t.datetime "updated_at"
-    t.integer  "translation_id"
+    t.integer "translation_id"
+    t.index ["translation_id"], name: "index_problems_on_translation_id"
   end
 
-  add_index "problems", ["translation_id"], name: "index_problems_on_translation_id"
-
   create_table "translations", force: :cascade do |t|
-    t.string   "title"
-    t.text     "content"
+    t.string "title"
+    t.text "content"
     t.datetime "created_at"
     t.datetime "updated_at"
-    t.integer  "problem_id"
+    t.integer "problem_id"
+    t.index ["problem_id"], name: "index_translations_on_problem_id"
   end
 
-  add_index "translations", ["problem_id"], name: "index_translations_on_problem_id"
-
 end