diff --git a/src/App.tsx b/src/App.tsx
index f7fe958..fc8dd6b 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -1,4 +1,4 @@
-import React from 'react';
+import React, {useReducer} from 'react';
 import styled from 'styled-components';
 import {TodosFooter} from './components/TodosFooter';
 import {TodosHeader} from './components/TodosHeader';
@@ -6,6 +6,7 @@ import {OnSubmit, TodoInput} from './components/TodoInput';
 import {TodoList} from './components/TodoList';
 import {Todo} from './types';
 import {TodoStatusBar} from './components/TodoStatusBar';
+import {OnTodoChange} from './components/TodoItem';
 
 export const AppContainer = styled.div`
   display: flex;
@@ -22,11 +23,29 @@ export interface AppState {
 
 export const App: React.FC = () => {
   const [todos, setTodos] = React.useState<Todo[]>([]);
+  const [congratsVisibility, setCongratsVisibility] = React.useState('none');
+  type CounterAction = {type: 'ADD'} | {type: 'REMOVE'} | {type: 'INITIAL'};
+  const [totalDone, dispatchDoneCounter] = useReducer(
+    (state: number, action: CounterAction): number => {
+      switch (action.type) {
+        case 'ADD':
+          return state + 1;
+        case 'REMOVE':
+          return state - 1;
+        case 'INITIAL':
+          return todos.filter(todo => todo.done).length;
+        default:
+          return 0;
+      }
+    },
+    0
+  );
 
   React.useEffect(() => {
     (async () => {
       const response = await fetch('http://localhost:3001/todos');
       setTodos(await response.json());
+      dispatchDoneCounter({type: 'INITIAL'});
     })();
   }, []);
 
@@ -54,15 +73,46 @@ export const App: React.FC = () => {
     return '';
   };
 
+  const updateTodo: OnTodoChange = async (todo: Todo) => {
+    const response = await fetch(`http://localhost:3001/todos/${todo.id}`, {
+      method: 'PUT',
+      headers: {
+        'Content-Type': 'application/json',
+      },
+      body: JSON.stringify(todo),
+    });
+    if (!response.ok) {
+      window.alert(
+        `Unexpected error ${response.status}: ${response.statusText}`
+      );
+      return todo;
+    }
+    let totalDoneCount = todos.filter(todo => todo.done).length;
+    if (todo.done && totalDoneCount === todos.length) {
+      setCongratsVisibility('flex');
+    }
+    dispatchDoneCounter(todo.done ? {type: 'ADD'} : {type: 'REMOVE'});
+    return todo;
+  };
+
   return (
     <AppContainer className='App'>
       <TodosHeader>
-        <TodoStatusBar total={todos.length} />
+        <TodoStatusBar
+          total={todos.length}
+          totalDone={totalDone}
+          // TODO: create a new component for the banner instead of adding in both header and footer
+          congratsBannerVisibility={congratsVisibility}
+        />
       </TodosHeader>
       <TodoInput onSubmit={createTodo} />
-      <TodoList todos={todos} />
+      <TodoList todos={todos} todoChange={updateTodo} />
       <TodosFooter>
-        <TodoStatusBar total={todos.length} />
+        <TodoStatusBar
+          total={todos.length}
+          totalDone={totalDone}
+          congratsBannerVisibility={'none'}
+        />
       </TodosFooter>
     </AppContainer>
   );
diff --git a/src/components/TodoItem.tsx b/src/components/TodoItem.tsx
index 5694ebf..0d6ab59 100644
--- a/src/components/TodoItem.tsx
+++ b/src/components/TodoItem.tsx
@@ -10,17 +10,31 @@ const TodoCheckbox = styled.input`
   margin-right: 8px;
 `;
 
+export type OnTodoChange = (todo: Todo) => Promise<Todo>;
+
 export interface TodoItemProps {
   todo: Todo;
+  todoChange: OnTodoChange;
   className?: string;
 }
 
-const _TodoItem: React.FC<TodoItemProps> = ({todo, className}) => (
-  <li data-cy='TodoItem' className={className}>
-    <TodoCheckbox type='checkbox' checked={todo.done} />
-    <TodoText done={todo.done}>{todo.text}</TodoText>
-  </li>
-);
+const _TodoItem: React.FC<TodoItemProps> = ({todo, className, todoChange}) => {
+  const handleChange = (event: React.ChangeEvent<HTMLInputElement>) => {
+    todo.done = event.target.checked.valueOf();
+    todoChange(todo);
+  };
+
+  return (
+    <li data-cy='TodoItem' className={className}>
+      <TodoCheckbox
+        type='checkbox'
+        checked={todo.done}
+        onChange={handleChange}
+      />
+      <TodoText done={todo.done}>{todo.text}</TodoText>
+    </li>
+  );
+};
 
 export const TodoItem = styled(_TodoItem)`
   display: flex;
diff --git a/src/components/TodoList.test.tsx b/src/components/TodoList.test.tsx
new file mode 100644
index 0000000..26e3e81
--- /dev/null
+++ b/src/components/TodoList.test.tsx
@@ -0,0 +1,22 @@
+import React from 'react';
+import {render, screen} from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import {TodoList} from './TodoList';
+import {Todo} from '../types';
+
+test('populates TodoList and assert they are listed by most recent', async () => {
+  const user = userEvent.setup();
+
+  const todos: Todo[] = [
+    { id: '1', text: 'First todo', done: false, createdTimestamp: 1000 },
+    { id: '2', text: 'Second todo', done: false, createdTimestamp: 2000 }
+  ];
+
+  const onChange = jest.fn(async () => todos[0]);
+
+  render(<TodoList todos={todos} todoChange={onChange} />);
+  const items = screen.getAllByRole('listitem');
+
+  expect(items[0]).toHaveTextContent("Second todo");
+  expect(items[1]).toHaveTextContent("First todo");
+});
diff --git a/src/components/TodoList.tsx b/src/components/TodoList.tsx
index 4ed9568..6f4672f 100644
--- a/src/components/TodoList.tsx
+++ b/src/components/TodoList.tsx
@@ -1,19 +1,22 @@
 import React from 'react';
 import styled from 'styled-components';
 import {Todo} from '../types';
-import {TodoItem} from './TodoItem';
+import {TodoItem, OnTodoChange} from './TodoItem';
 
 export interface TodoListProps {
   todos: Array<Todo>;
   className?: string;
+  todoChange: OnTodoChange;
 }
 
-const _TodoList: React.FC<TodoListProps> = ({todos, className}) => {
+const _TodoList: React.FC<TodoListProps> = ({todos, className, todoChange}) => {
   return (
     <ul data-cy='TodoList' className={className}>
-      {todos.map((todo, index) => (
-        <TodoItem key={index} todo={todo} />
-      ))}
+      {todos
+        .sort((t1, t2) => t2.createdTimestamp - t1.createdTimestamp)
+        .map((todo, index) => (
+          <TodoItem key={index} todo={todo} todoChange={todoChange} />
+        ))}
     </ul>
   );
 };
diff --git a/src/components/TodoStatusBar.tsx b/src/components/TodoStatusBar.tsx
index 2f36f7f..2a51d97 100644
--- a/src/components/TodoStatusBar.tsx
+++ b/src/components/TodoStatusBar.tsx
@@ -6,17 +6,34 @@ const InfoBar = styled.div`
   justify-content: space-between;
 `;
 
+const CongratulationsBanner = styled.div<{isCongratsBannerVisible: string}>`
+  display: ${props => props.isCongratsBannerVisible || 'none'};
+  justify-content: center;
+`;
+
 export interface TodoStatusBarProps {
   className?: string;
   total: number;
+  totalDone: number;
+  congratsBannerVisibility: string;
 }
 
-const _TodoStatusBar: React.FC<TodoStatusBarProps> = ({className, total}) => (
+const _TodoStatusBar: React.FC<TodoStatusBarProps> = ({
+  className,
+  total,
+  totalDone,
+  congratsBannerVisibility,
+}) => (
   <div data-cy='TodoStatusBar' className={className}>
     <InfoBar>
       <span>Total: {total}</span>
-      <span>Done: 0</span>
+      <span>Done: {totalDone}</span>
     </InfoBar>
+    <CongratulationsBanner isCongratsBannerVisible={congratsBannerVisibility}>
+      <span>
+        Congratulations, you're all set! You've done everything on your list.
+      </span>
+    </CongratulationsBanner>
   </div>
 );