diff --git a/.ruby-version b/.ruby-version
index a3ec5a4..eb39e53 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.2
+3.3
diff --git a/Gemfile b/Gemfile
index 0e4fcbb..b6c7b89 100644
--- a/Gemfile
+++ b/Gemfile
@@ -15,6 +15,6 @@ group :development do
   gem "ruby-lsp" # TODO: Set up ruby-lsp
 
   # types
-  gem "rbs-inline"
-  gem "steep"
+  # gem "rbs-inline"
+  # gem "steep"
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index 67b7e7e..39ffe75 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,55 +1,19 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (7.1.3.4)
-      base64
-      bigdecimal
-      concurrent-ruby (~> 1.0, >= 1.0.2)
-      connection_pool (>= 2.2.5)
-      drb
-      i18n (>= 1.6, < 2)
-      minitest (>= 5.1)
-      mutex_m
-      tzinfo (~> 2.0)
-    ast (2.4.2)
-    base64 (0.2.0)
     bigdecimal (3.1.8)
-    concurrent-ruby (1.3.3)
-    connection_pool (2.4.1)
-    csv (3.3.0)
-    drb (2.2.1)
-    ffi (1.17.0-arm64-darwin)
-    fileutils (1.7.2)
-    i18n (1.14.5)
-      concurrent-ruby (~> 1.0)
-    json (2.7.2)
     language_server-protocol (3.17.0.3)
-    listen (3.9.0)
-      rb-fsevent (~> 0.10, >= 0.10.3)
-      rb-inotify (~> 0.9, >= 0.9.10)
     logger (1.6.0)
     minitest (5.24.0)
-    mutex_m (0.2.0)
-    parser (3.3.3.0)
-      ast (~> 2.4.1)
-      racc
     phlex (1.10.3)
     prism (0.30.0)
-    racc (1.8.0)
     rack (3.1.4)
     rackup (2.1.0)
       rack (>= 3)
       webrick (~> 1.8)
-    rainbow (3.1.1)
     rake (13.2.1)
-    rb-fsevent (0.11.2)
-    rb-inotify (0.11.1)
-      ffi (~> 1.0)
     rbs (3.5.1)
       logger
-    rbs-inline (0.4.0)
-      prism (>= 0.29, < 0.31)
-      rbs (~> 3.5.0)
     roda (3.81.0)
       rack
     ruby-lsp (0.17.4)
@@ -57,33 +21,11 @@ GEM
       prism (>= 0.29.0, < 0.31)
       rbs (>= 3, < 4)
       sorbet-runtime (>= 0.5.10782)
-    securerandom (0.3.1)
     sequel (5.81.0)
       bigdecimal
     sorbet-runtime (0.5.11460)
     sqlite3 (2.0.2-arm64-darwin)
-    steep (1.7.1)
-      activesupport (>= 5.1)
-      concurrent-ruby (>= 1.1.10)
-      csv (>= 3.0.9)
-      fileutils (>= 1.1.0)
-      json (>= 2.1.0)
-      language_server-protocol (>= 3.15, < 4.0)
-      listen (~> 3.0)
-      logger (>= 1.3.0)
-      parser (>= 3.1)
-      rainbow (>= 2.2.2, < 4.0)
-      rbs (>= 3.5.0.pre)
-      securerandom (>= 0.1)
-      strscan (>= 1.0.0)
-      terminal-table (>= 2, < 4)
-    strscan (3.1.0)
-    terminal-table (3.0.2)
-      unicode-display_width (>= 1.1.1, < 3)
     tilt (2.4.0)
-    tzinfo (2.0.6)
-      concurrent-ruby (~> 1.0)
-    unicode-display_width (2.5.0)
     webrick (1.8.1)
 
 PLATFORMS
@@ -96,12 +38,10 @@ DEPENDENCIES
   phlex
   rackup
   rake
-  rbs-inline
   roda
   ruby-lsp
   sequel
   sqlite3
-  steep
   tilt
 
 BUNDLED WITH
diff --git a/lib/rank_king/open_skill.rb b/lib/rank_king/open_skill.rb
index 6487474..34a5fc9 100644
--- a/lib/rank_king/open_skill.rb
+++ b/lib/rank_king/open_skill.rb
@@ -79,7 +79,7 @@ module RankKing
       }
     end
 
-    def rating(mu: nil, sigma: nil)
+    def rating(mu: nil, sigma: nil) #:: Rating
       mu ||= @mu
       sigma ||= mu / @z
       Rating.new(mu: mu.to_f, sigma: sigma.to_f)