This is great, but one of the principles of spaced repetition learning is not to group the information by category. This reduces the effectiveness, because the learner will know that their guess will be limited to one of the four primary categories. The originator of spaced repetition theory and practice had only one set of cards for everything. Once you have learned the initial content meaningfully in context preferably with mnemonics, the best way to test recall is by mixing content. In this way, you are not primed for a specific type of answer. For the theory and recent scholarship I highly recommend the book, “Make it Stick” particularly the chapter on interleaving review. Thanks for the post.