Practise repository for the tutorials and to practise on to your heart's content. Be aware that every so often pull requests might be accepted and are merged with the main repository which will affect what's displayed (especially if it's your pull request that gets accepted/merged). You cannot break anything - please practise until you feel confident to do the first task for your assignment. Pay attention to the phrasing of the assignment task to make sure you request the correct pull for the main repository!