This website lets you work on Faded Parsons Problems, a type of programming exercise where you rearrange blocks of code and fill in blanks to create a working program. You can learn more about Faded Parsons Problems in Nate Weinman's CHI 2021 paper.
The problems hosted here are all in Python 3 and checked for correctness using doctests.
Here's a (non-comprehensive) list of the problem hosted here:
If you're a teacher and would like to host your own problems, check the Github repository for more instructions.