★★★☆☆ The app's design is good, but the mnemonics are...I'm sorry, but they are not very useful to learners. If you have to stretch or modify the katakana to make pictures out of them, then the pictures are not representative of the katakana, so they are not helpful in remembering them. The app functions well and has a pretty good UI, but I don't think it is very helpful for the aforementioned reason.