To do list web app Flask - Python

Create a web app that takes input from the user one item at a time in a textbox and adds them to a todolist when the user clicks the submit button. The webapp should work with an unlimited number of items. Allow a user to mark certain items in the todo list as 'done' which should display a separate list called 'Completed items' when the user hits submit. Items not marked as 'done' should still appear in the todo list.