I know you're looking for advice on your app idea but I just want to throw this in. I'm concerned that you're memorizing math. In my experience flash cards only

I know you're looking for advice on your app idea but I just want to throw this in. I'm concerned that you're memorizing math. In my experience flash cards only reduce your ability to learn (and apply) math. You need to understand the reasons behind the operations you're performing and understand why they applied for a particular problem. This builds intuition which is much more long-term than memorization. Memorizing equations for an exam helps you for that exam only (typically). Being able to quickly derive the equation any time you need will help you forever. This is harder but only at first. You'll thank yourself. As for the app, go for it! Just don't use it for math and preferably don't pitch it as a aid for math students. You'll only be hurting them.