diff --git a/db/languages.yml b/db/languages.yml
index 12645ff2..1b4765b8 100644
--- a/db/languages.yml
+++ b/db/languages.yml
@@ -6,174 +6,177 @@
 # interpreter_command is executed directly using 'isolate' (so the first argument must be the full path to the interpreter)
 
 c++:
-  :name: "C++"
-  :lexer: c++
-  :compiled: yes
-  :interpreted: no
-  :current: c++17
-  :extension: .cpp
-  :source_filename: program
-  :exe_extension: .exe
-  :processes: 1
-  :variants:
-    c++03:  # deprecated
-      :name: "C++03"
-      :compiler: g++
-      :compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu++03 -O2 -o %{output} %{source} -lm"
+  name: "C++"
+  lexer: c++
+  compiled: yes
+  interpreted: no
+  current: c++17
+  extension: .cpp
+  source_filename: program
+  exe_extension: .exe
+  processes: 1
+  variants:
+    c++03: # deprecated
+      name: "C++03"
+      compiler: g++
+      compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu++03 -O2 -o %{output} %{source} -lm"
     c++11:
-      :name: "C++11"
-      :compiler: g++
-      :compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu++11 -O2 -o %{output} %{source} -lm"
-    c++14:  # Changes since C++11: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1319r0.html
-      :name: "C++14"
-      :compiler: g++
-      :compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu++14 -O2 -o %{output} %{source} -lm"
-    c++17:  # Changes since C++14: https://isocpp.org/files/papers/p0636r0.html
-      :name: "C++17"
-      :compiler: g++
-      :compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu++17 -O2 -o %{output} %{source} -lm"
+      name: "C++11"
+      compiler: g++
+      compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu++11 -O2 -o %{output} %{source} -lm"
+    c++14: # Changes since C++11: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1319r0.html
+      name: "C++14"
+      compiler: g++
+      compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu++14 -O2 -o %{output} %{source} -lm"
+    c++17: # Changes since C++14: https://isocpp.org/files/papers/p0636r0.html
+      name: "C++17"
+      compiler: g++
+      compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu++17 -O2 -o %{output} %{source} -lm"
 c:
-  :name: "C"
-  :lexer: c
-  :compiled: yes
-  :interpreted: no
-  :current: c11
-  :extension: .c
-  :source_filename: program
-  :exe_extension: .exe
-  :processes: 1
-  :variants:
-    c99:  # deprecated
-      :name: C99
-      :compiler: gcc
-      :compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu99 -O2 -o %{output} %{source} -lm"
-    c11:  # Changes since c99: https://en.wikipedia.org/wiki/C11_(C_standard_revision)
-      :name: C11
-      :compiler: gcc
-      :compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu11 -O2 -o %{output} %{source} -lm"
+  name: "C"
+  lexer: c
+  compiled: yes
+  interpreted: no
+  current: c11
+  extension: .c
+  source_filename: program
+  exe_extension: .exe
+  processes: 1
+  variants:
+    c99: # deprecated
+      name: C99
+      compiler: gcc
+      compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu99 -O2 -o %{output} %{source} -lm"
+    c11: # Changes since c99: https://en.wikipedia.org/wiki/C11_(C_standard_revision)
+      name: C11
+      compiler: gcc
+      compiler_command: "%{compiler} --version | head -n 1 1>&2 && %{compiler} -std=gnu11 -O2 -o %{output} %{source} -lm"
 
 java:
-  :name: Java
-  :lexer: java
-  :compiled: yes
-  :interpreted: yes
-  :current: java11
-  :extension: .java
-  :source_filename: Main
-  :exe_extension: .jar
-  :processes: 0
-  :variants:
+  name: Java
+  lexer: java
+  compiled: yes
+  interpreted: yes
+  current: java11
+  extension: .java
+  source_filename: Main
+  exe_extension: .jar
+  processes: 0
+  variants:
     java6:
-      :name: Java 1.6  # deprecated (note: uses '-source 1.6', which will be removed in a future JDK release)
-      :compiler: javac;jar
-      :compiler_command: '%{compiler[0]} -version | head -n 1 1>&2 && %{compiler[0]} -O -source 1.6 -J-Xms16m -J-Xmx256m %{source} && %{compiler[1]} cfe %{output} Main -C %{source_dir} .'
-      :interpreter: /usr/bin/java
-      :interpreter_command: '%{interpreter} -jar %{source}'
+      name: Java 1.6 # deprecated (note: uses '-source 1.6', which will be removed in a future JDK release)
+      compiler: javac;jar
+      compiler_command: "%{compiler[0]} -version | head -n 1 1>&2 && %{compiler[0]} -O -source 1.6 -J-Xms16m -J-Xmx256m %{source} && %{compiler[1]} cfe %{output} Main -C %{source_dir} ."
+      interpreter: /usr/bin/java
+      interpreter_command: "%{interpreter} -jar %{source}"
     java11:
-      :name: Java 11
-      :compiler: javac;jar
-      :compiler_command: '%{compiler[0]} -version | head -n 1 1>&2 && %{compiler[0]} -O -source 11 -J-Xms16m -J-Xmx256m %{source} && %{compiler[1]} cfe %{output} Main -C %{source_dir} .'
-      :interpreter: /usr/bin/java
-      :interpreter_command: '%{interpreter} -jar %{source}'
+      name: Java 11
+      compiler: javac;jar
+      compiler_command: "%{compiler[0]} -version | head -n 1 1>&2 && %{compiler[0]} -O -source 11 -J-Xms16m -J-Xmx256m %{source} && %{compiler[1]} cfe %{output} Main -C %{source_dir} ."
+      interpreter: /usr/bin/java
+      interpreter_command: "%{interpreter} -jar %{source}"
+
 haskell:
-  :name: Haskell
-  :lexer: haskell
-  :compiled: yes
-  :interpreted: no
-  :current: haskell2010
-  :extension: .hs
-  :source_filename: program
-  :exe_extension: .exe
-  :processes: 1
-  :variants:
+  name: Haskell
+  lexer: haskell
+  compiled: yes
+  interpreted: no
+  current: haskell2010
+  extension: .hs
+  source_filename: program
+  exe_extension: .exe
+  processes: 1
+  variants:
     haskell2010:
-      :name: "Haskell 2010"
-      :compiler: ghc
-      :compiler_command: '%{compiler} --version 1>&2 && %{compiler} --make -O2 -o %{output} %{source} -lm'
+      name: "Haskell 2010"
+      compiler: ghc
+      compiler_command: "%{compiler} --version 1>&2 && %{compiler} --make -O2 -o %{output} %{source} -lm"
+
 python:
-  :name: Python
-  :lexer: python
-  :compiled: no
-  :interpreted: yes
-  :current: python3.8
-  :extension: .py
-  :source_filename: program
-  :processes: 1
-  :interpreter_command: '%{interpreter} %{source}'
-  :compiler_command: '%{interpreter} -m py_compile %{source}'
-  :variants:
-    python2:  # deprecated - Python 2 reached end-of-life in late 2019
-      :name: "Python 2.7"
-      :interpreter: /usr/bin/python2
-    python3.4:  # deprecated
-      :name: "Python 3.4"
-      :interpreter: /usr/bin/python3.4
+  name: Python
+  lexer: python
+  compiled: no
+  interpreted: yes
+  current: python3.8
+  extension: .py
+  source_filename: program
+  processes: 1
+  interpreter_command: "%{interpreter} %{source}"
+  compiler_command: "%{interpreter} -m py_compile %{source}"
+  variants:
+    python2: # deprecated - Python 2 reached end-of-life in late 2019
+      name: "Python 2.7"
+      interpreter: /usr/bin/python2
+    python3.4: # deprecated
+      name: "Python 3.4"
+      interpreter: /usr/bin/python3.4
     python3.8:
-      :name: "Python 3.8"
-      :interpreter: /usr/bin/python3.8
+      name: "Python 3.8"
+      interpreter: /usr/bin/python3.8
     pypy3:
-      :name: "Python 3.6 (PyPy 7.3)"
-      :interpreter: /usr/bin/pypy3
+      name: "Python 3.6 (PyPy 7.3)"
+      interpreter: /usr/bin/pypy3
 
 ruby:
-  :name: Ruby
-  :lexer: ruby
-  :compiled: no
-  :interpreted: yes
-  :current: ruby2.2
-  :extension: .rb
-  :source_filename: program
-  :processes: 2 # ruby seems to have an extra process
-  :interpreter_command: '%{interpreter} %{source}'
-  :compiler_command: '%{interpreter} -c %{source}'
-  :variants:
+  name: Ruby
+  lexer: ruby
+  compiled: no
+  interpreted: yes
+  current: ruby2.2
+  extension: .rb
+  source_filename: program
+  processes: 2 # ruby seems to have an extra process
+  interpreter_command: "%{interpreter} %{source}"
+  compiler_command: "%{interpreter} -c %{source}"
+  variants:
     ruby2.2:
-      :name: "Ruby 2.2"
-      :interpreter: /usr/bin/ruby2.2
+      name: "Ruby 2.2"
+      interpreter: /usr/bin/ruby2.2
+
 j:
-  :name: J
-  :lexer: text
-  :compiled: no
-  :interpreted: yes
-  :current: j8
-  :extension: .ijs
-  :source_filename: program
-  :processes: 3 # needed for system/main/stdlib.ijs to shell out to uname
-  :interpreter_command: '%{interpreter} %{source}'
-  :variants:
+  name: J
+  lexer: text
+  compiled: no
+  interpreted: yes
+  current: j8
+  extension: .ijs
+  source_filename: program
+  processes: 3 # needed for system/main/stdlib.ijs to shell out to uname
+  interpreter_command: "%{interpreter} %{source}"
+  variants:
     j8:
-      :name: "J 8.03"
-      :interpreter: /usr/bin/ijconsole-8.0.3
+      name: "J 8.03"
+      interpreter: /usr/bin/ijconsole-8.0.3
 
 javascript:
-  :name: JavaScript
-  :lexer: javascript
-  :compiled: no
-  :interpreted: yes
-  :current: v8_8
-  :extension: .js
-  :source_filename: program
-  :interpreter_command: '%{interpreter} %{source}'
-  :variants:
+  name: JavaScript
+  lexer: javascript
+  compiled: no
+  interpreted: yes
+  current: v8_8
+  extension: .js
+  source_filename: program
+  interpreter_command: "%{interpreter} %{source}"
+  variants:
     v8_8:
-      :name: "JavaScript (V8 8.1)"
-      :interpreter: /usr/local/bin/d8
-      :processes: 9
+      name: "JavaScript (V8 8.1)"
+      interpreter: /usr/local/bin/d8
+      processes: 9
 
 csharp:
-  :name: "C#"
-  :lexer: csharp
-  :compiled: yes
-  :interpreted: yes
-  :current: csharp8
-  :extension: .cs
-  :source_filename: program
-  :exe_extension: .exe
-  :processes: 5
-  :interpreter: /usr/local/bin/dotnet-exec  # custom shell script
-  :variants:
+  name: "C#"
+  lexer: csharp
+  compiled: yes
+  interpreted: yes
+  current: csharp8
+  extension: .cs
+  source_filename: program
+  exe_extension: .exe
+  processes: 5
+  interpreter: /usr/local/bin/dotnet-exec # custom shell script
+  variants:
     csharp8:
-      :name: "C# 8.0"
-      :compiler: dotnet-csc  # custom shell script (also prints SDK version number)
-      :compiler_command: '%{compiler} %{source} -optimize+ -out:%{output} -langversion:8.0 -nologo'
-      :interpreter_command: '%{interpreter} %{source}'
+      name: "C# 8.0"
+      compiler: dotnet-csc # custom shell script (also prints SDK version number)
+      compiler_command: "%{compiler} %{source} -optimize+ -out:%{output} -langversion:8.0 -nologo"
+      interpreter_command: "%{interpreter} %{source}"
diff --git a/db/seeds.rb b/db/seeds.rb
index 70863652..d19dc2f2 100644
--- a/db/seeds.rb
+++ b/db/seeds.rb
@@ -6,81 +6,12 @@
 #   cities = City.create([{ :name => 'Chicago' }, { :name => 'Copenhagen' }])
 #   Mayor.create(:name => 'Daley', :city => cities.first)
 
-if !User.exists?(0) # code in this block to be fixed
-  # rootuser = User.new()
-  # rootuser.id = 0
-  # rootuser.name = "System"
-  # rootuser.username = "system"
-  # rootuser.email = "system@nztrain.com"
-  # rootuser.encrypted_password = ""
-  # rootuser.save
-  # no users in user table, create a user
-  # rootuser = User.new({:id => 0, :name => "Root User", :username => "root", :email => "root@nztrain.com", :encrypted_password => "Need an encrypted password here"})
-end
+# We use different seed files for different environments, meaning we don't
+# have to worry about development data leaking into prod (in the unlikely
+# event we ever ran db:seed in prod), and vice-vesa.
 
-["superadmin", "admin", "staff", "organiser", "author"].each do |role|
-  Role.find_or_create_by(name: role)
-end
+# db/seeds/common.rb is things we want in every environment
+require_relative Rails.root.join("db/seeds/common")
 
-# give superadmin status to set everything up
-rootuser = nil
-
-if User.exists?(0)
-  rootuser = User.find(0) # if a root user exists and is zeroth (this is for security because normally users get positive integers as id) user in users table, give superadmin status
-end
-
-if rootuser && rootuser.username == "root"
-  superadmin = Role.find_by_name("superadmin")
-  superadmin.users.push(rootuser) unless superadmin.users.include?(rootuser)
-end
-
-["system/mailer/email", "system/mailer/password", "recaptcha/public_key", "recaptcha/private_key"].each do |setting|
-  Setting.find_or_create_by(key: setting)
-end
-
-setting = Setting.find_or_create_by(key: "submissions/shuffle")
-setting.update_attributes(value: Random.new.rand(2E9.to_i).to_s) if setting.value.nil?
-
-# create a special group called Everyone
-if !Group.exists?(0)
-  everyone = Group.new
-  everyone.id = 0
-  everyone.name = "Everyone"
-  everyone.owner_id = 0
-  everyone.save
-end
-
-if !User.exists?(0)
-  everyone = Group.find(0)
-  user = User.new
-  user.id = 0
-  user.username = "System"
-  user.name = "System"
-  user.email = "nztrain@gmail.com"
-  user.password = "somepassword" # ensure validation succeeds
-  user.encrypted_password = "$2a$10$KpSeaHGXoXEwdrERTFVCPo428a2s2r4ZazR999X9abc22368nneen" # set password hash so no known password matches the hash
-  user.groups.push(everyone)
-  user.save
-end
-
-languages = YAML.load(File.read(File.expand_path("db/languages.yml", Rails.root)))
-langfields = %i[name compiler compiler_command interpreter interpreter_command lexer interpreted compiled extension source_filename exe_extension processes]
-languages.each do |grpid, grpcfg|
-  groupopts = grpcfg.slice(:name)
-  group = LanguageGroup.where(identifier: grpid).first_or_create!
-  group.update_attributes(groupopts)
-
-  grpcfg[:variants].each do |langid, langcfg|
-    langopts = langcfg.reverse_merge(grpcfg).slice(*langfields).merge(group_id: group.id)
-    language = Language.where(identifier: langid).first_or_create!
-    language.update_attributes(langopts)
-  end
-
-  group.update_attributes(current_language_id: group.languages.find_by_identifier(grpcfg[:current]).id)
-end
-
-ProblemSeries.where(identifier: "COCI").first_or_create!.update_attributes(name: "Croatian Open Competition in Informatics", importer_type: "Problems::COCI::Importer")
-
-Entity.find_or_create_by(name: "New Zealand Olympiad in Informatics", entity_type: "Organisation") do |entity|
-  entity.entity_id = Organisation.create.id
-end
+env_seed_path = Rails.root.join("db/seeds/#{Rails.env}.rb")
+require_relative env_seed_path if File.exist?(env_seed_path)
diff --git a/db/seeds/common.rb b/db/seeds/common.rb
new file mode 100644
index 00000000..6c7fe2d5
--- /dev/null
+++ b/db/seeds/common.rb
@@ -0,0 +1,50 @@
+%w[superadmin admin staff organiser author].each do |name|
+  Role.find_or_create_by!(name: name)
+end
+
+rootuser = User
+  .create_with(
+    username: "System",
+    name: "System",
+    email: "nztrain@gmail.com",
+    password: SecureRandom.base64(18),
+    roles: [Role.find_by!(name: "superadmin")]
+  )
+  .find_or_create_by!(id: 0)
+
+["system/mailer/email", "system/mailer/password", "recaptcha/public_key", "recaptcha/private_key"].each do |setting|
+  Setting.find_or_create_by!(key: setting)
+end
+
+Setting
+  .create_with(value: Random.new.rand(2E9.to_i).to_s)
+  .find_or_create_by!(key: "submissions/shuffle")
+
+Group
+  .create_with(
+    name: "Everyone",
+    owner: rootuser
+  )
+  .find_or_create_by(id: 0)
+
+languages = YAML.safe_load(File.read(File.expand_path("db/languages.yml", Rails.root))).with_indifferent_access
+langfields = %i[name compiler compiler_command interpreter interpreter_command lexer interpreted compiled extension source_filename exe_extension processes]
+languages.each do |grpid, grpcfg|
+  groupopts = grpcfg.slice(:name)
+  group = LanguageGroup.where(identifier: grpid).first_or_create!
+  group.update_attributes(groupopts)
+
+  grpcfg[:variants].each do |langid, langcfg|
+    langopts = langcfg.reverse_merge(grpcfg).slice(*langfields).merge(group_id: group.id)
+    language = Language.where(identifier: langid).first_or_create!
+    language.update_attributes(langopts)
+  end
+
+  group.update_attributes(current_language_id: group.languages.find_by_identifier(grpcfg[:current]).id)
+end
+
+ProblemSeries.where(identifier: "COCI").first_or_create!.update_attributes(name: "Croatian Open Competition in Informatics", importer_type: "Problems::COCI::Importer")
+
+Entity.find_or_create_by(name: "New Zealand Olympiad in Informatics", entity_type: "Organisation") do |entity|
+  entity.entity_id = Organisation.create.id
+end
diff --git a/db/seeds/development.rb b/db/seeds/development.rb
new file mode 100644
index 00000000..2427db30
--- /dev/null
+++ b/db/seeds/development.rb
@@ -0,0 +1,26 @@
+# db/seeds/common.rb always runs before this, so we can assume
+# roles etc defined there exist already.
+
+# Add a nice, memorable, boring set of users for local development
+%w[user admin superadmin].each do |username|
+  User
+    .create_with(
+      name: username.capitalize,
+      email: "#{username}@example.com",
+      password: "password",
+      confirmed_at: Time.current
+    ).find_or_create_by!(
+      username: username
+    )
+end
+
+User.find_by!(username: "admin").update!(roles: [Role.find_by!(name: "admin")])
+User.find_by!(username: "superadmin").update!(roles: [Role.find_by!(name: "superadmin")])
+
+# A problem & set
+problem_set = ProblemSet.find_or_create_by!(name: "Example problems")
+Problem
+  .create_with(problem_sets: [problem_set])
+  .find_or_create_by!(name: "Example problem")
+
+problem_set.group_associations.find_or_create_by!(group: Group.find_by(name: "Everyone"))