To those preparing for the JLPT exam, ganbare!
I made a simple web-app to prepare for the grammar section during commutes. Should work well on iOS or android under home screen-mode. I even put a custom icon in the web-app.
Used simple bootstrap css classes, along with jquery to develop the logic and interface, and painstakingly created raw data from my Japanese grammar textbook during my studying which I then translated to JSON via a quick python script. I found this actually helped my studying since if I just rote learn by reading, I will simply fall asleep, so typing in all the grammars made me study to some extent. The app then forces me to memorise what I supposedly already studied by doing random card quizzes on the entire grammar set.
Some other screenshots: