Cookie clicker is a game where you click a cookie to get more cookies. With these cookies you can buy machines that generate cookies for you to buy more machines. This game gets very repetitive and often you have to get off your computer and just let it sit.
https://cookie-clicker.co/
Quill is a terrible "game" where you are assigned different topics and you have to answer many questions and keep answering more questions.
https://quill.org/