In the last question of the test (subsection 9) in tactic ninja/windmill, it's possible for Black to do a little bit better than what is proposed: after 4. Tf7+, Black should not play Kg8 but Bf6. This leads to 5. Bxf6+ Kg8 6. Txd7 Rxf6, and Black captures an extra piece compared to the proposed variation. The conclusion does not change though, Black is completely lost. And the conclusion on the course does not change either, it's a really great course.