We don't require a particular commitment - it really depends on what you want to get out of the course. If you want to fully participate, you should plan on 4-8 hours/topic. Readings and reflections could take anywhere from 1-4 (or even more) hours. You might end up discussing some of your work with other learners. And the activities are relatively open ended as well. It's possible to build a small Scratch project in 30 minutes, or spend a full day refining it. Also, there is no requirement to complete everything.