diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 0000000..2dbfaac
Binary files /dev/null and b/.DS_Store differ
diff --git a/elm-todo/Todo.elm b/elm-todo/Todo.elm
index 3a07b24..ba6dd21 100755
--- a/elm-todo/Todo.elm
+++ b/elm-todo/Todo.elm
@@ -45,7 +45,6 @@ type alias Model =
 type alias Entry =
     { description : String
     , completed : Bool
-    , editing : Bool
     , id : Int
     }
 
@@ -62,7 +61,6 @@ newEntry : String -> Int -> Entry
 newEntry desc id =
     { description = desc
     , completed = False
-    , editing = False
     , id = id
     }
 
@@ -76,8 +74,6 @@ to them.
 -}
 type Msg
     = UpdateNewEntryField String
-    | EditingEntry Int Bool
-    | UpdateEntry Int String
     | Add
     | Delete Int
     | DeleteAllCompleted
@@ -102,28 +98,6 @@ update msg model =
         UpdateNewEntryField str ->
             { model | newEntryField = str }
 
-        EditingEntry id isEditing ->
-            let
-                updateEntry t =
-                    if t.id == id then
-                        { t | editing = isEditing }
-                    else
-                        t
-
-                focus =
-                    Dom.focus ("todo-" ++ toString id)
-            in
-                { model | entries = List.map updateEntry model.entries }
-
-        UpdateEntry id task ->
-            let
-                updateEntry t =
-                    if t.id == id then
-                        { t | description = task }
-                    else
-                        t
-            in
-                { model | entries = List.map updateEntry model.entries }
 
         Check id isCompleted ->
             let
@@ -229,7 +203,7 @@ viewKeyedEntry todo =
 viewEntry : Entry -> Html Msg
 viewEntry todo =
     li
-        [ classList [ ( "completed", todo.completed ), ( "editing", todo.editing ) ] ]
+        [ classList [ ( "completed", todo.completed ) ] ]
         [ div
             [ class "view" ]
             [ input
@@ -240,7 +214,7 @@ viewEntry todo =
                 ]
                 []
             , label
-                [ onDoubleClick (EditingEntry todo.id True) ]
+                []
                 [ text todo.description ]
             , button
                 [ class "destroy"
@@ -248,16 +222,6 @@ viewEntry todo =
                 ]
                 []
             ]
-        , input
-            [ class "edit"
-            , value todo.description
-            , name "title"
-            , id ("todo-" ++ toString todo.id)
-            , onInput (UpdateEntry todo.id)
-            , onBlur (EditingEntry todo.id False)
-            , onEnter (EditingEntry todo.id False)
-            ]
-            []
         ]
 
 
@@ -313,8 +277,7 @@ viewControlsClear entriesCompleted =
 infoFooter : Html msg
 infoFooter =
     footer [ class "info" ]
-        [ p [] [ text "Double-click to edit a todo" ]
-        , p []
+        [ p []
             [ text "Written by "
             , a [ href "https://github.com/evancz" ] [ text "Evan Czaplicki" ]
             ]
diff --git a/ruby-todo/.DS_Store b/ruby-todo/.DS_Store
new file mode 100644
index 0000000..2ca3fe3
Binary files /dev/null and b/ruby-todo/.DS_Store differ
diff --git a/ruby-todo/lib/engine.rb b/ruby-todo/lib/engine.rb
index a257c20..7f7c38a 100644
--- a/ruby-todo/lib/engine.rb
+++ b/ruby-todo/lib/engine.rb
@@ -5,8 +5,7 @@ def self.run(*args)
 
   def self.run_with_history(model, messages)
     messages.map do |msg|
-      msg.apply_to(model)
-      model
+      model = msg.apply_to(model)
     end
   end
 end
diff --git a/ruby-todo/lib/messages.rb b/ruby-todo/lib/messages.rb
index abe85de..f9a3660 100644
--- a/ruby-todo/lib/messages.rb
+++ b/ruby-todo/lib/messages.rb
@@ -2,13 +2,16 @@ module Msg
 
   class Add
     def apply_to(model)
+      newEntries = model.entries.clone
+
       unless model.new_entry_field.blank?
-        model.entries << Entry.new(
-          description: model.new_entry_field,
-          id: model.next_id)
+        newEntries << Entry.new(
+         description: model.new_entry_field,
+         id: model.next_id)
       end
-      model.next_id += 1
-      model.new_entry_field = ""
+      
+      newNextId = model.next_id + 1
+      newModel = Model.new(next_id: newNextId, new_entry_field: "", entries: newEntries)
     end
   end
 
@@ -20,7 +23,7 @@ def initialize(str)
     attr_reader :str 
 
     def apply_to(model)
-      model.new_entry_field = str
+      newModel = Model.new(entries: model.entries.clone, next_id: model.next_id, new_entry_field: str)
     end
   end
 
@@ -32,11 +35,17 @@ def initialize(id, is_completed)
     attr_reader :id, :is_completed 
 
     def apply_to(model)
-      model.entries.each do |entry|
-        if entry.id == id
-          entry.completed = is_completed
-        end
+      newEntries = model.entries.map do |entry|
+          newEntry = entry
+            if entry.id == id
+                newEntry = Entry.new(description: entry.description, id: entry.id, completed: is_completed)
+            end
+            newEntry
       end
+      
+      newModel = Model.new(next_id: model.next_id, new_entry_field: model.new_entry_field, entries: newEntries)
+      
+      newModel
     end
   end
 
@@ -48,14 +57,21 @@ def initialize(id)
     attr_reader :id 
 
     def apply_to(model)
-      model.entries.reject! { |e| e.id == id }
+        
+        newModel = Model.new(next_id: model.next_id, new_entry_field: model.new_entry_field, entries: model.entries.clone)
+
+        newModel.entries.reject! { |e| e.id == id }
+        newModel
     end
   end
 
   class DeleteAllCompleted
     def apply_to(model)
-      model.entries.reject!(&:completed)
+        
+        newEntries = model.entries.clone
+        newEntries.reject!(&:completed)
+        
+        newModel = Model.new(next_id: model.next_id, new_entry_field: model.new_entry_field, entries: newEntries)
     end
   end
-
 end
diff --git a/ruby-todo/lib/model.rb b/ruby-todo/lib/model.rb
index 75a6085..e64ca6a 100644
--- a/ruby-todo/lib/model.rb
+++ b/ruby-todo/lib/model.rb
@@ -5,7 +5,7 @@ def initialize(entries: [], new_entry_field: "", next_id: nil)
       (entries.lazy.map(&:id).max || -1) + 1
   end
 
-  attr_accessor :entries, :new_entry_field, :next_id
+  attr_reader :entries, :new_entry_field, :next_id
 
   def ==(other)
     !other.nil? &&
@@ -20,7 +20,7 @@ def initialize(id:, description:, completed: false)
     @description, @id, @completed = description, id, completed
   end
 
-  attr_accessor :description, :completed, :id
+  attr_reader :description, :completed, :id
 
   def ==(other)
     !other.nil? &&
diff --git a/ruby-todo/test/.DS_Store b/ruby-todo/test/.DS_Store
new file mode 100644
index 0000000..7e87deb
Binary files /dev/null and b/ruby-todo/test/.DS_Store differ
diff --git a/ruby-todo/test/todo_test.rb b/ruby-todo/test/todo_test.rb
index f7436c7..ddd4de3 100644
--- a/ruby-todo/test/todo_test.rb
+++ b/ruby-todo/test/todo_test.rb
@@ -91,7 +91,7 @@
   end
 
   it "supports time travel" do
-    skip "Mutable model does not support time travel"
+      #  skip "Mutable model does not support time travel"
 
     actual_history = Engine.run_with_history(Model.new, [
       Msg::UpdateNewEntryField.new("go forward in time"),
diff --git a/swift-todo/Sources/Todo/Engine.swift b/swift-todo/Sources/Todo/Engine.swift
index e3b14a7..1b0f709 100644
--- a/swift-todo/Sources/Todo/Engine.swift
+++ b/swift-todo/Sources/Todo/Engine.swift
@@ -13,9 +13,10 @@ struct Engine {
     }
 
     static func runWithHistory(on model: Model, applying messages: [Message]) -> [Model] {
+        var curModel = model
         return messages.map { message in
-          message.apply(to: model)
-          return model
+          curModel = message.apply(to: curModel)
+          return curModel
         }
     }
 }
diff --git a/swift-todo/Sources/Todo/Message.swift b/swift-todo/Sources/Todo/Message.swift
index 92dd868..80d0a0e 100644
--- a/swift-todo/Sources/Todo/Message.swift
+++ b/swift-todo/Sources/Todo/Message.swift
@@ -14,30 +14,34 @@ enum Message {
     case delete(Int)
     case deleteAllCompleted
 
-    func apply(to model: Model) {
+    func apply(to model: Model) -> Model {
+        var newModel = model
         switch(self) {
             case .add:
                 if !model.newEntryField.isBlank() {
-                    model.entries.append(Entry(id: model.nextID, description: model.newEntryField))
+                    var newEntries = model.entries
+                    newEntries.append(Entry(id: model.nextID, description: model.newEntryField))
+                    newModel.entries = newEntries
                 }
-                model.nextID += 1
-                model.newEntryField = ""
-
+                newModel.nextID += 1
+                newModel.newEntryField = ""
+            
             case .updateNewEntryField(let str):
-                model.newEntryField = str
+                newModel.newEntryField = str
 
             case .check(let id, let isCompleted):
-                for entry in model.entries {
-                    if(entry.id == id) {
-                        entry.completed = isCompleted
+                for i in newModel.entries.indices {
+                    if(newModel.entries[i].id == id) {
+                        newModel.entries[i].completed = isCompleted
                     }
                 }
-
+            
             case .delete(let id):
-                model.entries.remove { $0.id == id }
+                newModel.entries.remove { $0.id == id }
 
             case .deleteAllCompleted:
-                model.entries.remove { $0.completed }
+                newModel.entries.remove { $0.completed }
         }
+        return newModel
     }
 }
diff --git a/swift-todo/Sources/Todo/Model.swift b/swift-todo/Sources/Todo/Model.swift
index 1cca801..d50d863 100644
--- a/swift-todo/Sources/Todo/Model.swift
+++ b/swift-todo/Sources/Todo/Model.swift
@@ -1,4 +1,4 @@
-class Model {
+struct Model {
     var entries: [Entry]
     var newEntryField: String
     var nextID: Int
@@ -11,7 +11,7 @@ class Model {
     }
 }
 
-class Entry {
+struct Entry {
     var id: Int
     var description: String
     var completed: Bool
diff --git a/swift-todo/Tests/TodoTests/TodoTests.swift b/swift-todo/Tests/TodoTests/TodoTests.swift
index 9220517..7346f27 100644
--- a/swift-todo/Tests/TodoTests/TodoTests.swift
+++ b/swift-todo/Tests/TodoTests/TodoTests.swift
@@ -77,7 +77,7 @@ class TodoTests: XCTestCase {
          XCTAssertEqual([11], newModel.entries.map { $0.id })
      }
 
-/*
+
      func testTimeTravel() {
         let actualHistory = Engine.runWithHistory(on: Model(), applying: [
              .updateNewEntryField("go forward in time"),
@@ -145,6 +145,6 @@ class TodoTests: XCTestCase {
              XCTAssertEqual(expected, actual, "History mismatch at step \(index)")
          }
     }
-*/
+
 
 }