diff --git a/README.md b/README.md
index 964af82..aa8e1a9 100644
--- a/README.md
+++ b/README.md
@@ -1106,11 +1106,10 @@ export default combineReducers<TodosState, TodosAction>({
         return [...state, action.payload];
 
       case TOGGLE:
-        return state.map(
-          item =>
-            item.id === action.payload
-              ? { ...item, completed: !item.completed }
-              : item
+        return state.map(item =>
+          item.id === action.payload
+            ? { ...item, completed: !item.completed }
+            : item
         );
 
       default:
diff --git a/playground/package-lock.json b/playground/package-lock.json
index 609a2fa..c528fd1 100644
--- a/playground/package-lock.json
+++ b/playground/package-lock.json
@@ -14236,9 +14236,9 @@
       "integrity": "sha512-NLpRc/FY+jPfWL0aUXQzjxPyF0Xug2om6akaoRLQ18KGwP2yYNBJu9vkv2q1q+Cx/+edy2Qf6O8xXnYY/xwz1A=="
     },
     "typescript": {
-      "version": "3.1.6",
-      "resolved": "https://registry.npmjs.org/typescript/-/typescript-3.1.6.tgz",
-      "integrity": "sha512-tDMYfVtvpb96msS1lDX9MEdHrW4yOuZ4Kdc4Him9oU796XldPYF/t2+uKoX0BBa0hXXwDlqYQbXY5Rzjzc5hBA==",
+      "version": "3.0.3",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-3.0.3.tgz",
+      "integrity": "sha512-kk80vLW9iGtjMnIv11qyxLqZm20UklzuR2tL0QAnDIygIUIemcZMxlMWudl9OOt76H3ntVzcTiddQ1/pAAJMYg==",
       "dev": true
     },
     "uglify-js": {
diff --git a/playground/package.json b/playground/package.json
index b7e838e..b42dc31 100644
--- a/playground/package.json
+++ b/playground/package.json
@@ -56,7 +56,7 @@
     "ts-jest": "22.4.6",
     "tslint": "5.12.1",
     "tslint-react": "3.6.0",
-    "typescript": "3.1.6",
+    "typescript": "3.0.3",
     "webpack": "3.11.0",
     "webpack-blocks": "1.0.0"
   }
diff --git a/playground/src/features/todos/reducer.ts b/playground/src/features/todos/reducer.ts
index 4282be1..47f720c 100644
--- a/playground/src/features/todos/reducer.ts
+++ b/playground/src/features/todos/reducer.ts
@@ -19,11 +19,10 @@ export default combineReducers<TodosState, TodosAction>({
         return [...state, action.payload];
 
       case TOGGLE:
-        return state.map(
-          item =>
-            item.id === action.payload
-              ? { ...item, completed: !item.completed }
-              : item
+        return state.map(item =>
+          item.id === action.payload
+            ? { ...item, completed: !item.completed }
+            : item
         );
 
       default:
diff --git a/playground/src/store/create-reducer.ts b/playground/src/store/create-reducer.ts
new file mode 100644
index 0000000..78f1e78
--- /dev/null
+++ b/playground/src/store/create-reducer.ts
@@ -0,0 +1,36 @@
+import { ActionType, getType } from 'typesafe-actions';
+
+import { Todo } from '../features/todos/models';
+import * as actions from '../features/todos/actions';
+
+export type TodosAction = ActionType<typeof actions>;
+
+function createReducer<S, A extends { type: string }>(
+  initialState: S,
+  handlers: {
+    [P in A['type']]?: A extends { type: P }
+      ? (state: S, action: A) => S
+      : never
+  }
+) {
+  return (state: S = initialState, action: A): S => {
+    if (handlers.hasOwnProperty(action.type)) {
+      return (handlers as any)[action.type](state, action);
+    } else {
+      return state;
+    }
+  };
+}
+
+export const todos = createReducer<Todo[], TodosAction>([], {
+  ['todos/ADD' as 'todos/ADD']: (state, action) => {
+    return [...state, action.payload];
+  },
+  ['todos/TOGGLE']: (state, action) => {
+    return state.map(item =>
+      item.id === action.payload
+        ? { ...item, completed: !item.completed }
+        : item
+    );
+  },
+});